A plain-English guide to the markers on a full blood count, iron studies, ferritin, thyroid, common vitamin and mineral tests (vitamin D, B12, folate, magnesium, zinc and calcium) and reproductive hormones by cycle phase: what each one does, example NHS ranges, what a low or high result can be linked to, what can help, and what to ask your GP.
Many women have real physical and psychological symptoms while their blood tests are reported as normal. That does not mean the symptoms are imagined, and it is reasonable to keep asking questions. There are several well-recognised reasons:
What can help: keep a symptom and cycle diary (the symptom tracker can do this), ask for your actual numbers rather than just "normal", ask what the next step is, and ask about repeating tests or looking at trends. If you are not making progress, you can ask for a second opinion or a referral. See our GP appointment guide.
Checks your red cells (which carry oxygen), white cells (which fight infection) and platelets (which help blood to clot).
| Marker | What it does | Example NHS range (adult women) |
|---|---|---|
| Haemoglobin (Hb) | The protein in red blood cells that carries oxygen around your body. | 115 to 165 g/L |
| Red blood cell count (RBC) | The number of red cells in your blood. | 3.80 to 5.80 x10¹²/L |
| Haematocrit (HCT or PCV) | The share of your blood that is made up of red cells. | 0.37 to 0.47 L/L |
| Mean cell volume (MCV) | The average size of your red cells. | 80 to 100 fL |
| Mean cell haemoglobin (MCH) | The average amount of haemoglobin in each red cell. | 27 to 32 pg |
| Mean cell haemoglobin concentration (MCHC) | How concentrated the haemoglobin is inside your red cells. | 33 to 36 g/dL |
| Red cell distribution width (RDW) | How much your red cells vary in size. | 11 to 15 % |
| White blood cell count (WBC) | The total of all your infection-fighting cells. | 3.6 to 11.0 x10⁹/L |
| Neutrophils | The first line of defence against bacterial infections. | 1.8 to 7.5 x10⁹/L |
| Lymphocytes | White cells that help you respond to viruses and build immunity. | 1.0 to 4.0 x10⁹/L |
| Monocytes | White cells that clear up infection and damaged cells. | 0.2 to 0.8 x10⁹/L |
| Eosinophils | White cells involved in allergies and in fighting some parasites. | 0.1 to 0.4 x10⁹/L |
| Basophils | The least common white cell. | 0.02 to 0.10 x10⁹/L |
| Platelets | Small cells that help your blood to clot. | 140 to 400 x10⁹/L |
The protein in red blood cells that carries oxygen around your body. It is the main test for anaemia.
Anaemia. Common causes include iron deficiency (for example from heavy periods, pregnancy or blood loss in childbirth), low vitamin B12 or folate, long-term illness and some inherited conditions. Tiredness, breathlessness, dizziness, palpitations and headaches can go with it.
Dehydration, smoking, living at altitude, and some lung or bone marrow conditions.
If iron is the cause: iron-rich food with vitamin C, tea, coffee and dairy kept away from iron-rich meals, and treating the cause, such as heavy periods. Iron tablets only if your GP advises, with a recheck. Low B12 or folate need their own treatment. Do not wait for a routine appointment if you are breathless at rest, have chest pain or faint.
Is this lower than my usual result? What is causing it? Was ferritin checked too? When should we repeat it?
The number of red cells in your blood. Together with haemoglobin and haematocrit it shows how much oxygen-carrying capacity you have.
Anaemia from iron, B12 or folate deficiency, blood loss or long-term illness. Pregnancy can lower it because blood volume increases.
Dehydration, smoking, and some bone marrow conditions.
It follows haemoglobin, so the focus is the cause. Drinking enough fluid before a test avoids a falsely high result.
Do my red cell numbers fit together with my haemoglobin and ferritin?
The share of your blood that is made up of red cells.
The same causes as a low haemoglobin, mainly anaemia.
Dehydration, smoking, and some bone marrow conditions.
Treat the cause of a low result. Being dehydrated can push it up.
Is this in line with my haemoglobin?
The average size of your red cells.
Small cells (microcytic): iron deficiency, thalassaemia trait and long-standing inflammation. A low MCV with a normal haemoglobin is worth asking about alongside ferritin.
Large cells (macrocytic): low vitamin B12 or folate, regular alcohol, an underactive thyroid, liver disease and some medicines.
Low: look at iron. High: ask about B12, folate and thyroid, and consider how much alcohol you drink. Foods rich in B12 include meat, fish, eggs, dairy and fortified foods. Folate is in green vegetables such as broccoli, Brussels sprouts and peas.
What does my MCV suggest? Should B12, folate, ferritin or thyroid be checked?
The average amount of haemoglobin in each red cell.
Iron deficiency, thalassaemia trait and long-standing inflammation. Often low when the MCV is low.
Usually seen with large red cells, for example in B12 or folate deficiency.
Focus on the cause, as for MCV.
Does this match my MCV and iron results?
How concentrated the haemoglobin is inside your red cells. Not every lab reports it.
Iron deficiency, thalassaemia trait and long-standing inflammation.
Uncommon. Sometimes an inherited red cell condition.
Focus on the cause. A single odd value with an otherwise normal count is rarely meaningful.
Is this result relevant alongside my other red cell results?
How much your red cells vary in size. Not every lab reports it.
Not usually a concern.
Iron, B12 or folate deficiency, recent blood loss and some bone marrow conditions. A mix of deficiencies can give a normal MCV but a high RDW.
Look for and treat the underlying deficiency, then recheck.
Could my RDW point to low iron, B12 or folate even if my MCV is normal?
The total of all your infection-fighting cells.
Some viral infections, certain medicines, autoimmune conditions, liver disease, heavy alcohol use, and some bone marrow conditions.
Infection, inflammation, stress, smoking, steroids and pregnancy. Rarely, a blood disorder.
The focus is the cause, not the number. Recheck when you are well if it was taken during an illness. Ask for a review if it stays outside the range.
Could an infection or medicine explain this? Should it be repeated, and when?
The first line of defence against bacterial infections.
Viral infections, some medicines and autoimmune conditions. Some people have naturally lower levels, which can vary between ethnic groups.
Bacterial infection, inflammation, physical stress, smoking and steroids.
Treat the cause. Recheck when well. Ask your GP about fever or repeated infections if the count is low.
Is this normal for me? Should it be repeated?
White cells that help you respond to viruses and build immunity.
Some viral infections, stress, steroids and some medicines.
Viral infections. Rarely, a blood condition.
Usually settles after an infection. Recheck if it stays outside the range.
Could a recent illness explain this?
White cells that clear up infection and damaged cells.
Rarely a concern on its own.
Some infections, inflammation and recovery from infection.
Recheck once you are well if raised.
Is this a one-off, or should it be repeated?
White cells involved in allergies and in fighting some parasites.
Rarely a concern on its own.
Allergies such as asthma, hay fever and eczema, drug reactions and parasites.
Ask whether your allergies or a new medicine could explain it.
Could allergies or a medicine explain this?
The least common white cell. Involved in allergic and inflammatory reactions.
Not usually a concern.
Rarely raised. Some allergies, inflammatory conditions and bone marrow conditions.
A slightly raised single result is rarely significant. Ask for a recheck if it persists.
Should this be repeated?
Small cells that help your blood to clot.
Viral infections, B12 or folate deficiency, alcohol, liver disease, some medicines and immune conditions. Tell your doctor about easy bruising, nosebleeds or bleeding gums.
Iron deficiency, infection, inflammation, recent surgery or bleeding. A raised platelet count can be a clue to low iron.
Treat the cause. If iron is low, restoring it often brings platelets down.
Could my platelets be linked to iron or inflammation?
Show how much iron is in your blood and how well it is being carried around. Best read together with ferritin.
| Marker | What it does | Example NHS range (adult women) |
|---|---|---|
| Serum iron | The iron travelling in your blood right now. | 9.0 to 30.4 µmol/L |
| Total iron binding capacity (TIBC) | How much iron your blood could carry. | 50 to 90 µmol/L |
| Transferrin | The protein made in the liver that carries iron around your blood. | 1.80 to 3.82 g/L |
| Transferrin saturation (TSAT) | The share of your transferrin that is carrying iron. | 16 to 40 % |
The iron travelling in your blood right now. It is not the same as your stores, and it changes through the day and after meals or supplements.
Iron deficiency and long-term illness or inflammation.
Iron tablets taken shortly before the test, haemochromatosis (too much iron) and iron poisoning.
On its own it is unreliable. Ask the lab whether to fast or pause iron supplements before a test. Do not start iron tablets because of a single result. Ask your GP to look at it with ferritin and transferrin saturation.
Was I meant to fast? Was this taken in the morning? What do my ferritin and transferrin saturation show?
How much iron your blood could carry. It reflects the amount of transferrin, the protein that carries iron.
Long-term illness, liver disease and iron overload.
Usually iron deficiency. The oral contraceptive pill can also raise it.
The focus is the cause. Tell the lab or your GP if you take the pill.
Do my TIBC and transferrin saturation point to low iron?
The protein made in the liver that carries iron around your blood.
Inflammation, liver disease, poor nutrition and iron overload.
Iron deficiency. It can also be higher with the contraceptive pill or in pregnancy.
The focus is the cause. A raised transferrin with low ferritin is a typical iron deficiency pattern.
What do my transferrin and ferritin show together?
The share of your transferrin that is carrying iron. About a third is typical.
Iron deficiency and long-term illness.
Iron overload such as haemochromatosis. One NHS lab flags more than 40% in women for further checks. Iron supplements can also raise it.
If it is low, ask about iron stores. If it is high, do not take iron and ask your GP about further tests.
Is my transferrin saturation low or high for a woman? Do I need further tests?
Your iron stores. Often the earliest marker to fall when iron is running low.
| Marker | What it does | Example NHS range (adult women) |
|---|---|---|
| Ferritin | The protein that stores iron. | 11 to 310 µg/L (one NHS lab) |
The protein that stores iron. It is the best single guide to your iron stores and is often the first marker to drop when iron is running low.
Iron deficiency, even if your haemoglobin is still normal. The 2021 British Society of Gastroenterology guideline suggests 45 µg/L as the best cut-off for iron deficiency, and below 15 µg/L is highly specific. Many labs flag only lower values, so a result can be "in range" and still low for you.
Inflammation, infection, liver disease and heavy alcohol use can push ferritin up. Iron overload is a less common cause. Because ferritin rises with inflammation, a normal result can be falsely reassuring.
Eat haem iron (red meat, poultry, fish) and non-haem iron (pulses, dark green leafy vegetables, fortified cereals and bread, dried fruit) and add vitamin C. Keep tea, coffee and dairy away from iron-rich meals. Treat the cause, such as heavy periods. If your GP prescribes iron tablets, treatment usually lasts about six months, with a recheck. The BSG guideline says treating symptomatic iron deficiency without anaemia is reasonable in premenopausal women.
What cut-off does your lab use? Is my level low for me? Was CRP checked to rule out inflammation? Would iron be worth trying, and when will we recheck?
Your thyroid helps set your energy, temperature, mood and cycle. The tests show how hard it is working and why.
| Marker | What it does | Example NHS range (adult women) |
|---|---|---|
| Thyroid stimulating hormone (TSH) | The signal from your pituitary gland telling your thyroid how much hormone to make. | 0.27 to 4.2 mU/L (non-pregnant adults) |
| Free thyroxine (free T4) | The active form of the main thyroid hormone. | About 12 to 22 pmol/L (some labs 8 to 18) |
| Free triiodothyronine (free T3) | The most active thyroid hormone. | About 3.1 to 6.8 pmol/L |
| Thyroid antibodies (TPO) | Antibodies that attack the thyroid. | Reported as negative or positive (cut-offs vary by lab) |
The signal from your pituitary gland telling your thyroid how much hormone to make. It is usually the first thyroid test. NICE recommends TSH alone for diagnosing and monitoring an underactive thyroid, and the lab adds free T4 when TSH is outside the range.
An overactive thyroid, too much thyroid medicine, or illness. Rarely a pituitary problem.
An underactive thyroid. A high TSH with a normal free T4 is called subclinical hypothyroidism. One NHS guideline suggests repeating a TSH of 4.2 to 10 in 3 to 6 months, and checking TPO antibodies if it is confirmed. Ranges are different in pregnancy.
Thyroid conditions are treated with medicine rather than diet. Iodine in food (dairy, fish, eggs) supports the thyroid, but take advice before kelp or high-dose iodine supplements. Tell the lab if you take biotin, because high-dose biotin can interfere with some tests.
Was free T4 checked? Should this be repeated, and when? Would thyroid antibodies help? Could my symptoms be thyroid-related?
The active form of the main thyroid hormone. It helps interpret TSH.
With a high TSH, an underactive thyroid. With a low or normal TSH, rarely a pituitary problem or illness.
An overactive thyroid, or too much thyroid medicine.
Medicine and monitoring are decided by your GP or endocrinologist.
How do my TSH and free T4 fit together? What is the plan?
The most active thyroid hormone. It is mainly used to help diagnose an overactive thyroid.
Often seen in illness. Rarely used on its own.
An overactive thyroid.
It is not usually needed unless TSH is low.
Is a free T3 needed in my case?
Antibodies that attack the thyroid. They help identify autoimmune thyroid conditions such as Hashimoto's thyroiditis and Graves' disease.
Negative is the usual result.
Positive suggests autoimmune thyroid disease and a higher chance that a borderline TSH will become underactive over time. Some people are positive without any thyroid problem. One NHS guideline suggests monitoring a borderline TSH yearly if TPO is positive and every 3 years if negative.
There is no diet that removes the antibodies. Regular monitoring matters more than the number.
What does a positive result mean for me, and how often should my thyroid be checked?
Nutrients that support your energy, mood, bones, immunity, hair and skin. These are often not part of a standard NHS blood test, so you may need to ask, and your GP will decide whether testing is useful. Blood levels of some (magnesium, zinc, calcium) do not always reflect what your body holds.
| Marker | What it does | Example NHS range (adult women) |
|---|---|---|
| Vitamin D (25-hydroxyvitamin D) | Helps your body absorb calcium for bones, teeth and muscles, and supports the immune system. | Below 25 low | 25 to 50 possibly low | above 50 sufficient nmol/L |
| Vitamin B12 | Needed to make red blood cells, for nerves and for DNA. | 180 to 914 ng/L (one NHS lab). Borderline 145 to 179. Low 144 or below |
| Folate (vitamin B9) | Helps make new cells and DNA, and works with B12 to make red blood cells. | Above 4.0 µg/L (one NHS lab) |
| Other B vitamins (B1, B2, B6) | Help turn food into energy and support nerves, skin and the brain. | Not routinely tested on the NHS |
| Magnesium | Supports muscles, nerves, heart rhythm, bone and energy production. | 0.70 to 1.00 mmol/L (one NHS lab) |
| Zinc | Supports the immune system, wound healing, skin, hair, taste and smell, and hormone function. | Varies by lab (not routinely tested). Use your report |
| Calcium (adjusted) | Needed for bones and teeth, muscle contraction, nerves and the heart. | About 2.20 to 2.60 mmol/L (varies by lab) |
Helps your body absorb calcium for bones, teeth and muscles, and supports the immune system. Most of it is made in your skin from sunlight.
Below 25 nmol/L is considered deficient, and 25 to 50 nmol/L may be inadequate in some people. Low levels can go with bone and muscle aches, weakness and tiredness. Over time it can lead to soft or fragile bones. Risk is higher with darker skin, covering up, little time outdoors, and in autumn and winter in the UK.
Very high levels almost always come from too many supplements. Too much can raise blood calcium, which can harm the kidneys and heart. Sunlight cannot cause an overdose.
NHS advice is that all adults consider a 10 microgram (400 IU) daily supplement through autumn and winter, and all year if you have little sun exposure. Food sources are oily fish, red meat, egg yolks and fortified foods, but food alone rarely covers it. Do not take more than 100 micrograms (4,000 IU) a day. If your result is low, your GP or pharmacist can advise on a treatment dose and when to recheck.
Is my level low enough to need a treatment dose? How long should I take it, and when will we recheck? Do my calcium and bone health need looking at?
Needed to make red blood cells, for nerves and for DNA. Your body stores it, so a shortfall can take a long time to appear.
Below about 145 ng/L suggests deficiency, and 145 to 180 ng/L is borderline. Causes include a vegan or vegetarian diet, pernicious anaemia and other absorption problems, some medicines such as metformin and long-term acid-reducing tablets, and weight-loss surgery. Symptoms can include tiredness, pins and needles, memory or mood changes, a sore tongue and breathlessness. Tell your GP about nerve symptoms, as these should be treated promptly. Levels also fall naturally in pregnancy.
Usually from supplements or injections. Occasionally raised in liver or blood conditions, so a persistently high result without supplements is worth discussing.
Meat, fish, milk, cheese, eggs and fortified cereals or yeast extract contain B12. Vegans need fortified foods or a supplement. NHS guidance is that 2 mg or less a day is unlikely to cause harm. If you are deficient, your GP will decide between tablets and injections and look for the cause. Folic acid on its own can hide B12 deficiency, so check B12 first.
Is this deficient or borderline? What is the cause? Do I need injections or tablets? Should I be tested for pernicious anaemia? When do we recheck?
Helps make new cells and DNA, and works with B12 to make red blood cells. Folate is not stored for long, so you need it regularly from food.
A poor diet, heavy alcohol use, absorption problems such as coeliac disease, pregnancy, and some medicines such as certain anti-epileptics. Serum folate can drop quickly after a poor few days of eating even when stores are fine. Low folate can cause anaemia with large red cells, tiredness and mouth soreness.
Usually from supplements. High folic acid can mask a B12 deficiency.
Eat leafy greens, broccoli, Brussels sprouts, peas, chickpeas, kidney beans and fortified cereals. Cooking in lots of water loses some folate, so steam or microwave. If you could become pregnant, NHS advice is a 400 microgram folic acid supplement daily before conception and until 12 weeks of pregnancy, with a higher dose advised for some women after speaking to a doctor. More than 1 mg a day should only be taken on medical advice.
Was B12 checked too? Could my diet, a medicine or a gut condition explain this?
Help turn food into energy and support nerves, skin and the brain. B6 also helps make red blood cells.
Rare in people who eat a varied diet. Heavy alcohol use, poor absorption and very restricted diets are the usual causes. Deficiency can cause tiredness, mouth soreness and skin changes.
Too much B6 from supplements (usually 200 mg a day or more, sometimes lower over a long time) can cause numbness and tingling in the hands and feet by damaging nerves. Most B vitamins are otherwise passed in urine.
Wholegrains, oats, fortified cereals, eggs, dairy, meat, fish, pulses, bananas, nuts and seeds are good sources. The NHS advises taking no more than 10 mg of B6 a day in supplements unless a doctor says so. Check the label of any B complex or "women's health" product, as many contain much more than this.
Do my symptoms or diet make it worth testing anything beyond B12 and folate?
Supports muscles, nerves, heart rhythm, bone and energy production. Only a small amount is in the blood, so a normal result does not rule out low stores.
Poor intake, heavy alcohol use, diarrhoea and absorption problems, and some medicines such as long-term acid-reducing tablets and some water tablets. Low levels can cause muscle cramps, twitching, tiredness, and in more severe cases heart rhythm changes. Magnesium is not a routine test, so it is usually only done when symptoms or other results suggest it.
Rare, and usually linked to kidney problems or heavy use of magnesium-containing laxatives or antacids.
Good food sources are spinach, nuts, seeds, pulses, wholemeal bread and brown rice. The NHS says up to 400 mg a day from supplements is unlikely to cause harm, but higher doses can cause diarrhoea. Speak to your GP before supplements if you have kidney problems or take other medicines.
Could a medicine be lowering my magnesium? Should calcium and potassium be checked as well?
Supports the immune system, wound healing, skin, hair, taste and smell, and hormone function.
Poor intake (a vegan diet with little pulses or nuts is a common reason), absorption problems and heavy alcohol use. Possible signs include slow wound healing, frequent infections, hair thinning, skin problems and changes in taste. Blood zinc can be low during illness or inflammation, and can change through the day and after eating, so results can be hard to interpret.
Nearly always from supplements. Long-term high doses can cause low copper, anaemia, nausea and stomach upset.
Meat, shellfish, dairy including cheese, eggs, bread, wholegrains, pulses and seeds contain zinc. Phytates in unprocessed grains and pulses reduce absorption, and soaking, sprouting or fermenting helps. The NHS advises not taking more than 25 mg a day of supplemental zinc unless a doctor says so. Zinc and iron supplements can compete, so ask a pharmacist how to space them.
Is a zinc test useful in my case? Could my diet, a medicine or a gut condition be affecting my levels?
Needed for bones and teeth, muscle contraction, nerves and the heart. Your body keeps blood calcium in a very tight range, so it is not a measure of how much is in your bones.
Low vitamin D, kidney problems, parathyroid problems and some medicines. It can cause tingling around the mouth and fingers, cramps and twitching. See a doctor urgently for severe cramps, spasms, or a fit.
Most often from an overactive parathyroid gland. Other causes include too much vitamin D or calcium supplements, dehydration and some medicines. It can cause thirst, passing a lot of urine, constipation, tiredness, low mood and kidney stones.
Adults need about 700 mg of calcium a day, which most people can get from food. Sources are milk, cheese, yoghurt, calcium-fortified plant drinks, tinned fish with soft bones, kale, okra and fortified bread. Spinach contains calcium but little of it is absorbed. The NHS says 1,500 mg or less a day from supplements is unlikely to cause harm. Do not start calcium or vitamin D supplements to fix an abnormal blood calcium. Your GP needs to find the cause first.
Was this the adjusted calcium? Should vitamin D, parathyroid hormone or kidney function be checked? Do I need to repeat it?
Helpful when periods are irregular, absent or heavy, when you have symptoms such as acne, excess hair, hot flushes or low mood, or when you are trying to conceive. Tests need to be timed to your cycle, so tell your GP which day of your cycle you are on and which contraception you use.
Reproductive hormones change a lot across a cycle, so a result only makes sense alongside the day it was taken. Day 1 is the first day of full bleeding. Example ranges below come from two NHS labs and differ slightly.
| Phase | What is happening | FSH (IU/L) | LH (IU/L) | Oestradiol (pmol/L) | Progesterone (nmol/L) |
|---|---|---|---|---|---|
| Follicular from day 1 to about day 13 in a 28-day cycle | Period, then eggs mature and oestrogen rises. Oestrogen and progesterone are at their lowest in the first days. | 3.9 to 8.8 | 2.1 to 10.9 (1 to 12) | 80 to 420 | Below 4 |
| Mid-cycle (ovulation) about day 14 | Oestrogen peaks, LH surges and an egg is released. | 4.5 to 22.5 | 19.2 to 103 (16 to 104) | 120 to 1,900 | Not used |
| Luteal about day 15 to 28 | Progesterone rises to prepare the womb lining. If there is no pregnancy, both hormones fall and a period starts. | 1.8 to 5.1 | 1.2 to 12.9 (1 to 12) | 130 to 900 | Above 12, and above 30 confirms ovulation |
| After menopause | The ovaries have stopped releasing eggs. | Above 30 | 16 to 66 (one lab) | Below 110 | Low |
| Marker | What it does | Example NHS range (adult women) |
|---|---|---|
| Follicle stimulating hormone (FSH) | Made by the pituitary gland to help eggs mature in the ovaries. | Follicular 3.9 to 8.8 | mid-cycle 4.5 to 22.5 | luteal 1.8 to 5.1 IU/L |
| Luteinising hormone (LH) | Triggers ovulation. | Follicular 1 to 12 | mid-cycle 16 to 104 | luteal 1 to 12 IU/L (another lab 2.1 to 10.9, 19.2 to 103, 1.2 to 12.9) |
| Oestradiol (oestrogen) | The main oestrogen before menopause. | Follicular 80 to 420 | mid-cycle 120 to 1,900 | luteal 130 to 900 pmol/L | after menopause below 110 |
| Progesterone | Made after ovulation by the empty egg follicle. | Follicular below 4 | luteal above 12 nmol/L | above 30 confirms ovulation |
| Testosterone (total) | An androgen that women make in smaller amounts in the ovaries and adrenal glands. | Below 2.7 nmol/L (one NHS lab) |
| Sex hormone binding globulin (SHBG) | A protein that carries sex hormones in the blood. | 19 to 145 nmol/L (under 50). 14 to 136 (over 50) |
| Prolactin | The hormone that triggers milk production. | Below 700 mU/L (one NHS lab) |
Made by the pituitary gland to help eggs mature in the ovaries. It rises when the ovaries respond less, which is why it is used when looking at early menopause.
Can be seen with hormonal contraception, very low body weight or heavy exercise, high stress, high prolactin, and pituitary problems. These can all stop periods or make them irregular.
Persistently above 30 IU/L (off hormonal contraception) fits with the ovaries slowing down. During perimenopause FSH swings from month to month, so one normal result does not rule it out. The NHS guideline is that women over 45 with typical symptoms are diagnosed on symptoms rather than a blood test. Under 45, two raised results 4 to 6 weeks apart are used (NICE NG23). A raised FSH does not mean you can stop contraception.
There is no food or supplement that reliably lowers FSH. Regular meals, enough energy, sleep, stress care and a healthy weight support normal cycles. If periods have stopped because of low weight, over-exercise or stress, discuss it with your GP. Symptoms in perimenopause can be eased, so ask about options including HRT.
On which day of my cycle was this taken? Was I on hormonal contraception? Should it be repeated? Do my symptoms point to perimenopause?
Triggers ovulation. A surge in LH around mid-cycle causes the egg to be released.
Hormonal contraception, low body weight, over-exercise, stress and pituitary problems.
A mid-cycle surge is normal. Outside that, high LH can be seen in PCOS, where the LH to FSH ratio may be raised (about 2 to 3 or higher), though this is only found in about half of cases and is not needed for diagnosis. It is also high after menopause.
The aim is to find the cause rather than change the number. If you have irregular periods, acne, excess hair or hair thinning, ask your GP about PCOS. Weight management, regular physical activity and a balanced diet can help some women with PCOS.
Which cycle day was this taken? Could it be PCOS? Do I need an ultrasound or other tests?
The main oestrogen before menopause. It builds the womb lining, supports bones, skin, mood and heart health and drives the LH surge.
Menopause and perimenopause, premature ovarian insufficiency, low body weight, over-exercise, hormonal contraception, breastfeeding and pituitary problems. Low oestrogen can cause irregular or absent periods, hot flushes, vaginal dryness, low mood, poor sleep and bone loss.
Normal around ovulation and in pregnancy. Persistently high levels can be seen with some ovarian conditions, certain medicines and in people taking oestrogen. Oestradiol varies a lot day to day, so a single reading is hard to interpret.
Blood tests are not generally used to diagnose menopause or to guide HRT dosing in women over 45. If symptoms affect your life, ask about treatment options. Weight-bearing exercise, calcium, vitamin D and not smoking support bone health when oestrogen is low.
What day of my cycle was this? Is it appropriate for that phase? Do my symptoms need treatment even if the result is within range?
Made after ovulation by the empty egg follicle. It prepares the womb lining and, if there is no pregnancy, falls so a period can start. It is mainly used to check whether you have ovulated.
A mid-luteal level below about 12 nmol/L suggests ovulation may not have happened, or the test was mistimed. Irregular cycles, PCOS, stress, low weight and perimenopause can all cause this. Hormonal contraception stops ovulation, so the test is not useful on it.
Above 30 nmol/L about 7 days before your next period confirms ovulation. It is also high in pregnancy.
Timing is everything. For a regular 28-day cycle the sample is taken on day 21, or 7 days before your next expected period. With irregular cycles it may be repeated weekly until your period starts. A level of 12 to 30 nmol/L is often repeated with better timing. Track your cycle in the symptom tracker to bring accurate dates.
Was this timed 7 days before my period? Should it be repeated? What is the plan if I am not ovulating?
An androgen that women make in smaller amounts in the ovaries and adrenal glands. It contributes to libido, energy, muscle and bone.
Falls with age, after menopause, after removal of the ovaries and with some medicines. Reference ranges for the low end are not well established in women, so a low result is hard to interpret on its own.
Most often PCOS. Signs include irregular periods, acne, excess facial or body hair and scalp hair thinning. One NHS guideline suggests repeating a result above 4 nmol/L with LH, FSH and SHBG and referring if it is confirmed. A very high result (6 nmol/L or more) needs prompt specialist review to look for other causes.
For PCOS, regular activity, a balanced diet and healthy weight can help. Medicines may help with symptoms such as acne, unwanted hair and irregular periods. Samples that sit unseparated can read falsely high, so use a proper lab.
Do I need SHBG and a free androgen index? Could this be PCOS? Do I need a referral?
A protein that carries sex hormones in the blood. It affects how much testosterone is "free" and active, and is used to work out the free androgen index.
Obesity, insulin resistance, an underactive thyroid and some medicines. A low SHBG makes more testosterone free, which can add to PCOS symptoms.
Oestrogen (including the pill), pregnancy, an overactive thyroid, liver disease and low body weight or anorexia.
Treat the cause. Insulin sensitivity improves with regular activity, whole foods and fibre, enough sleep and, if relevant, weight management. The contraceptive pill raises SHBG and can affect testosterone results, so tell your GP.
Does my SHBG change how I should read my testosterone? Could thyroid or insulin resistance be involved?
The hormone that triggers milk production. It also suppresses ovulation when raised.
Rarely a concern.
Pregnancy, breastfeeding, stress, a recent meal or exercise, an underactive thyroid, some medicines (including some antidepressants and antipsychotics), and benign pituitary growths. High prolactin can cause irregular or absent periods, milk from the breasts when not pregnant and headaches. Mild rises are often repeated.
Treat the cause. Rest before the test and avoid exercise and nipple stimulation beforehand. Tell your GP about medicines. Persistent high levels are usually treatable.
Could stress, a medicine or my thyroid explain this? Do I need a repeat or a scan?
Doctors look at patterns, not single numbers. These are examples of patterns your GP may consider. They are not a diagnosis.
| Pattern | What it may point to |
|---|---|
| Low haemoglobin, low MCV, low ferritin | Iron deficiency anaemia |
| Normal haemoglobin, low or low-normal ferritin | Low iron stores, which can still cause symptoms. Worth discussing if you feel unwell |
| Normal ferritin with raised CRP or other signs of inflammation | Ferritin may look better than your iron stores really are. Ask about transferrin saturation |
| High MCV, with or without anaemia | Low B12 or folate, thyroid, alcohol or liver causes |
| High RDW with a normal MCV | Possibly a mix of deficiencies, such as iron and B12 |
| High platelets with low iron | Iron deficiency can raise platelets |
| High TSH, normal free T4 | Possible subclinical hypothyroidism. Often repeated in 3 to 6 months |
| High TSH, low free T4 | An underactive thyroid pattern |
| Large red cells with low B12 or folate | Possible B12 or folate deficiency. Needs the cause found and the right treatment |
| Low vitamin D with aches or low mood in autumn and winter | Common in the UK. A GP or pharmacist can advise on a treatment dose |
| Abnormal calcium | Needs a cause found, often vitamin D, kidneys or parathyroid |
| Irregular periods with high testosterone, low SHBG, acne or excess hair | May fit with PCOS. Diagnosed using several criteria, not one test |
| Raised FSH on two tests 4 to 6 weeks apart (off hormonal contraception) under 45 | May point to premature ovarian insufficiency. Needs specialist advice |
| Mid-luteal progesterone above 30 nmol/L | Suggests you ovulated that cycle |
Macronutrients are not measured by these blood tests, but they affect many of the results above.
Take your results to your GP with a symptom diary and your questions.
GP appointment checklist Symptom tracker GP appointment guideExample ranges come from NHS laboratory pages and are not universal. Your result and its range depend on your lab.
BioHer provides educational information only. It is not medical advice, diagnosis or treatment, and it does not replace your GP or other healthcare professional. If symptoms feel urgent or severe, call 111 for urgent advice, or 999 in an emergency. Last updated 20 October 2026.