Symptom · Heavy periods
If you flood through protection, pass clots bigger than a ten-pence piece, bleed for more than seven days or plan your life around your period, you are losing more iron every month than you can replace from food. The problem is that the standard test for this, a full blood count, is the last thing to change. Iron stores empty first, and by the time haemoglobin falls you have been running on nothing for a year or more. That is why so many women with heavy periods are told their blood test was normal while feeling exhausted, breathless on stairs and unable to think straight. Ferritin is the number that tells the truth, and it is rarely measured.
Venous draw at 103 UK clinics or at home. Report within 48 hours of the lab receiving your sample. No GP referral.
Last reviewed 17 September 2026
The short answer
A blood test for heavy periods should measure ferritin with full iron studies (not just a blood count), a full thyroid panel with antibodies, and the hormone picture: oestradiol, FSH, LH, progesterone, prolactin, testosterone and SHBG. A coeliac screen is worth adding if iron will not come up, and clotting tests if the bleeding has been heavy since your very first period. Two thirds of the value is in one number: a ferritin below 30 means deficiency and explains the tiredness, and it is entirely possible to have that with a perfectly normal haemoglobin.
See a GP, not just a blood test, if
You bleed between periods or after sex, your periods changed suddenly, you are over 45 with new heavy bleeding, you bleed after the menopause, or you have pelvic pain or pressure. NICE recommends examination and usually a pelvic ultrasound for heavy menstrual bleeding, because fibroids, polyps, adenomyosis and, rarely, something more serious are found by imaging rather than by blood. A blood panel tells you what the bleeding has cost you and whether a thyroid or hormone problem is driving it. It does not look inside the uterus.
What to test
| Marker | Why it matters with heavy periods | What to look for | NHS checks it? | Panel |
|---|---|---|---|---|
| Ferritin | Your iron stores, and the first thing heavy bleeding empties. Low ferritin causes exhaustion, breathlessness, hair shedding, brain fog, restless legs and cold hands long before anaemia appears | Below 30 µg/L is deficiency; symptoms are common below 50; below 15 is severe. A normal haemoglobin does not rule any of this out | NICE recommends it for heavy bleeding, but in practice many women get only a blood count | All panels |
| Full iron studies and blood count | Transferrin saturation and iron-binding capacity show whether iron is genuinely low when ferritin is muddied by inflammation; the blood count shows whether you have tipped into anaemia | Transferrin saturation below 20%; haemoglobin below 120 g/L; small pale red cells (low MCV and MCH) are the classic iron picture | Blood count yes, full iron studies rarely | All panels |
| Thyroid (TSH, free T4, free T3, antibodies) | An underactive thyroid is a recognised cause of heavy periods, and it also causes the same fatigue, so it can hide behind the iron picture. Treating it often settles the bleeding | TSH above range, or above 2.5 with symptoms; free T3 low; positive TPO antibodies | TSH usually, if asked | All panels |
| Oestradiol, FSH, LH, progesterone | Cycles without ovulation produce unopposed oestrogen and a thick lining, which is the commonest hormonal reason for heavy bleeding in the years either side of 40. Perimenopause does exactly this | FSH rising with a fluctuating oestradiol; low luteal progesterone showing cycles are not ovulatory | Rarely; NICE advises against FSH over 45 | Core hormones in Advanced; complete set in Ultimate and Signature |
| Testosterone, SHBG, prolactin | Polycystic ovary syndrome causes irregular cycles that build a thick lining and then bleed heavily; a raised prolactin disrupts ovulation in the same way | Raised testosterone with a low SHBG; raised prolactin | Only if PCOS is suspected | Testosterone in Advanced; SHBG, prolactin and the full set in Ultimate and Signature |
| Coeliac screen (tTG-IgA) | Undiagnosed coeliac disease stops you absorbing the iron you eat, so stores stay empty however much you take. The reason iron treatment sometimes does not work | Positive tTG while still eating gluten | Only if gut symptoms are mentioned | Signature digestive profile |
| Clotting (von Willebrand screen) | Around 1 in 8 women with genuinely heavy periods has an inherited bleeding disorder, usually von Willebrand disease, and most are undiagnosed. Suspect it if periods have been heavy since the very first one, or you bruise and bleed easily elsewhere | Needs a specific clotting screen arranged by a GP or haematologist, not a standard panel | Only if asked for | Not in TrueVitals panels; ask your GP |
Thresholds are UK laboratory conventions, NICE and British Society for Haematology guidance. Your report reads each result against the others. Guides: ferritin and iron studies, thyroid, perimenopause, PCOS, hair loss and ferritin.
The thing that gets missed
Iron leaves the body in a fixed order. First the stores go, which is ferritin. Then the supply to the tissues tightens, which is transferrin saturation. Only at the end does the blood itself change, which is haemoglobin and the red cell size. A full blood count, the test most women are given, measures only that last stage. So a woman bleeding heavily for two years can have a haemoglobin of 128, be told everything is fine, and have a ferritin of 9 with every symptom of iron deficiency: the tiredness, the hair coming out in the shower, the breathlessness on the stairs, the fog, the cold, the restless legs at night. Iron deficiency without anaemia is a real diagnosis with real symptoms, and it is treated the same way. The only way to see it is to measure ferritin.
Pattern 1
The commonest result by far. Iron at the right dose, taken on alternate days with vitamin C and away from tea and coffee, which absorbs better than daily dosing. Retest at three months, and expect the symptoms to lift before the number is fully back.
Pattern 2
TSH raised, free T3 low, antibodies positive, ferritin low as a consequence. Treating the thyroid often reduces the bleeding, which then stops the iron loss. Both need addressing, and the order matters: this is a GP conversation with all three results in hand.
Pattern 3
Ferritin still under 30 after three months of proper supplementation. Either the bleeding is still outpacing the intake, which is a gynaecology conversation, or absorption is the problem, which points to coeliac disease or low stomach acid. The retest is what reveals it.
Which panel
Enough for most
Advanced
74 biomarkers · £269
Ferritin with full iron studies and blood count, full thyroid with antibodies, core sex hormones, vitamin D, B12, folate, hs-CRP, liver and kidney. Everything needed to explain the tiredness and rule out a thyroid cause.
View AdvancedUltimate
114 biomarkers · £349
Adds oestradiol, FSH, LH, progesterone, prolactin, SHBG and free testosterone, so the hormonal reason for the bleeding is visible too: perimenopause, PCOS or cycles that are not ovulating.
View UltimateSignature
230 biomarkers · £799
Processed by Randox. Adds the digestive profile including coeliac screening, for iron that will not come up despite treatment.
View SignatureClinic draw £19. At-home £39. If you still have cycles, days 2 to 5 give the clearest FSH and oestradiol; progesterone is read around day 21. Keep eating gluten before a coeliac screen. Pay monthly available.
Honest comparison
NICE guidance on heavy menstrual bleeding is good and worth knowing: a full blood count for everyone, ferritin where iron deficiency is suspected, and a discussion of treatment, which can start before any investigation. Ask for it, because it is free, and ask for ferritin by name rather than "a blood test", since that single word is the difference between an answer and a shrug. Thyroid, hormones and coeliac are tested only if you raise the symptoms that prompt them. Where a panel earns its place is when you have had the blood count, been told it was normal, and still feel awful; when you want the hormone picture as well as the iron one; or when you would rather not wait weeks for an appointment to ask for one number. If the bleeding itself is the problem rather than its cost, the GP route matters more than the blood, because treatment and a scan are what change it. What to ask your GP for.
After your result
What the bleeding has taken out of you (iron, and what that explains) and what might be driving it (thyroid, perimenopause, PCOS), each explained against the others and reviewed by a medical professional.
Alternate-day dosing with vitamin C absorbs better than daily and is easier on the stomach. A thyroid result, a hormone pattern or bleeding that needs treating or scanning belongs with your GP, and the report tells you which results to show them.
Ferritin should be climbing. If it is not, the bleeding is still outpacing the intake or absorption is the problem, and that is a different conversation. The second report is what distinguishes them. Retest plans.
FAQs
Ferritin with full iron studies and a blood count, a full thyroid panel with antibodies, and the sex hormones: oestradiol, FSH, LH, progesterone, prolactin, testosterone and SHBG. Add a coeliac screen if iron will not come up, and ask your GP about a clotting screen if your periods have been heavy since your first one.
Yes, and it is extremely common. Iron stores empty first and haemoglobin falls last, so you can have a completely normal blood count with a ferritin of 10 and every symptom of deficiency. Iron deficiency without anaemia is a real diagnosis and is treated the same way. Only ferritin shows it.
Below 30 µg/L is deficiency in a menstruating woman, and symptoms are common anywhere below 50. Many UK labs flag only below 15, which is why results in the 15 to 30 range are so often reported as normal. If ferritin is normal but hs-CRP is raised, inflammation may be inflating the number and transferrin saturation gives the truer picture.
Yes. An underactive thyroid is a recognised cause of heavy menstrual bleeding, and treating it often settles the bleeding. It also causes the same tiredness as the iron loss, so both need measuring to know which is doing what.
For ferritin, iron and thyroid, any day. For hormones, days 2 to 5 give the clearest FSH and oestradiol, and progesterone is read about seven days before your next period is due, usually around day 21 of a 28-day cycle. Take it in the morning and fast from 10pm if you are having Ultimate.
Most people replace stores with oral iron over about three months, taken on alternate days with vitamin C, which absorbs better than daily dosing. An infusion is a hospital decision, usually for severe deficiency, intolerance of tablets, or when absorption is the problem. Your report gives the figures to discuss with your GP.
Advanced and Ultimate reports are delivered within 48 hours of the laboratory receiving your sample. Signature takes around 12 working days.
Ferritin, full iron studies, thyroid and hormones in one venous draw, at 103 UK clinics or at home, with a report within 48 hours that explains the tiredness and what to do about it.
Ferritin · Hair loss · Always tired · Perimenopause · Find a clinic
.png)