Coeliac Disease and Anaemia: Iron, B12 and Folate

For a lot of people, coeliac disease is found not in the gut but in the blood. You feel tired in a way that sleep doesn’t fix, maybe a little breathless on the stairs or paler than usual — and a routine blood test comes back showing iron-deficiency anaemia. Track down why the iron is low, and coeliac disease turns out to be the reason. It’s one of the most common ways the condition comes to light, often long before anyone suspects the small intestine.

This page goes deeper on the blood chapter of our Coeliac Beyond the Gut guide: what iron, vitamin B12 and folate do, why coeliac disease so often pulls them down, and — the reassuring part — why they usually climb back up once you’re on a gluten-free diet. Read it as an association and a common presentation, not something to worry about happening to you.

Why anaemia is so often the first sign

Iron, folate and vitamin B12 are the raw materials your body uses to make healthy red blood cells. When they run short, you can become anaemic — fewer or smaller red cells, less oxygen carried around — which shows up as fatigue, breathlessness, pale skin, brittle nails or a racing heart. In coeliac disease, the reason those raw materials run short is absorption: the gluten-driven immune reaction damages the lining of the upper small intestine, and that is precisely where iron and folate are taken up from food.

Because the damage can be quietly doing this for years, anaemia is sometimes the only sign of coeliac disease — no bloating, no diarrhoea, no obvious tummy trouble at all. That’s why national guidance takes unexplained anaemia seriously: NICE guideline NG20 recommends offering a test for coeliac disease to anyone with unexplained iron-deficiency anaemia, and Coeliac UK lists it among the most common ways the condition is picked up in adults. If your iron is low and no one can say why, coeliac disease is one of the things worth ruling in or out.

The three nutrients that most often run low

Iron — the usual one

Iron is absorbed mainly in the duodenum and the very start of the small intestine — the stretch that tends to be most inflamed in untreated coeliac disease. So iron-deficiency anaemia is the classic blood finding. It can leave you drained, foggy and cold-handed, and it responds well once the gut starts to heal and, where needed, iron stores are topped up under medical guidance.

Folate — often low too

Folate (vitamin B9) is absorbed a little further along, in the upper jejunum, which is also frequently affected. Low folate is common at diagnosis and can cause a different pattern of anaemia, with larger-than-normal red cells. One thing worth knowing: in many countries ordinary wheat flour and breakfast cereals are fortified with folic acid and iron, so a gluten-free diet can actually deliver less of both unless you plan for it. That’s one of the quiet reasons a coeliac-aware dietitian is so useful.

Vitamin B12 — less common, still worth checking

Vitamin B12 is absorbed lower down, in the last part of the small intestine (the terminal ileum), which coeliac disease damages less often. So B12 deficiency is less common than low iron or folate — but it does happen, and because it can affect nerves as well as blood, it’s part of the standard panel your clinic checks. If it’s low, it’s easily corrected.

What your blood tests are checking

You don’t need to decode the numbers yourself — your GP does that — but it helps to know what’s being looked at. A full blood count measures your haemoglobin and the size of your red cells (small cells point to iron; large cells point to folate or B12). Ferritin shows how much iron you have in the bank, while folate and B12 are measured directly. Most people with coeliac disease are offered an annual review that includes these, so shortfalls get spotted and put right over time — something Coeliac UK and the British Society of Gastroenterology both build into follow-up care.

How it usually gets better

Here’s the encouraging throughline. The core treatment for coeliac disease — a strict, lifelong gluten-free diet, meaning food at or below the Codex standard of no more than 20 ppm (20 mg/kg) of gluten — lets the small intestine heal. As the lining recovers, it goes back to absorbing iron, folate and B12 properly, and blood levels tend to rise on their own over the following months. Where stores are very low, your clinician may add a course of iron, folate or B12 to speed things up while the gut catches up, then recheck your bloods to confirm the trend.

A word on supplements: it’s best not to start high-dose iron on your own. Too much can upset your stomach and can muddy the picture your doctor is trying to read, so let your GP or dietitian guide the dose and check it’s working. Alongside any tablets, building iron- and folate-rich foods into everyday meals — pulses, eggs, leafy greens, nuts and seeds, and pairing plant iron with a little vitamin C to help it absorb — keeps the tank topped up naturally.

Iron, folate and B12 at a glance

When to see your GP

Unexplained tiredness or anaemia is always worth investigating rather than pushing through — so if you feel persistently drained, breathless or run-down, ask your GP for a blood test and let them find the cause. If coeliac disease hasn’t been ruled out, mention it, because testing is straightforward.

If you already have a coeliac diagnosis and your iron or folate stays low despite a strict gluten-free diet, that’s a flag to follow up too. Sometimes it points to small amounts of gluten still getting in; sometimes it’s a separate cause entirely, such as heavy periods or another gut issue. Either way, it’s a conversation for your GP, gastroenterologist or dietitian — not something to file under “just coeliac.”

Keep exploring

• Coeliac Beyond the Gut — the whole-body map this page belongs to.
• Coeliac Disease and Your Liver — raised liver enzymes that usually settle on a gluten-free diet.
• Coeliac Disease, the Spleen and Vaccinations — hyposplenism and when vaccines may be offered.
• Coeliac Follow-Up Care — your annual review, blood tests and nutrient checks, explained.
• Your First 90 Days With Coeliac Disease — settling into life after diagnosis.
• Coeliac Diagnosis & Medical FAQ — the questions people ask around testing.

Frequently asked questions

This page is general information, not medical advice. Anaemia and low nutrient levels are associations and common presentations of coeliac disease rather than certainties, and everyone’s situation is different — discuss your own blood results and any supplements with your GP, gastroenterologist or a coeliac-aware dietitian.

Sources & standards: Coeliac UK (iron, vitamin B12 and folate; anaemia as a presentation; annual review and the gluten-free diet); NICE guideline NG20 (coeliac disease: recognition, assessment and management, including testing in unexplained iron-deficiency anaemia); the British Society of Gastroenterology (BSG) guidelines on the diagnosis and management of adult coeliac disease and follow-up; the Codex Alimentarius gluten-free standard of no more than 20 ppm (20 mg/kg) of gluten; and AOECS (Association of European Coeliac Societies). Last verified: 2026-07-21.