Gut health, coeliac disease and hair: when the problem is absorption

20 December 2025  ·  6 min read  ·  Reviewed for accuracy September 2026

Occasionally a woman does everything right — the iron, the protein, the vitamin D — and her ferritin will not move and her hair will not recover. When that happens, the problem is often not what she is eating but what she is absorbing.

Coeliac disease

An autoimmune reaction to gluten that damages the lining of the small intestine, where iron, folate, zinc, calcium and fat-soluble vitamins are absorbed. It affects around one in a hundred people in the UK, most undiagnosed, and it clusters in women, in the years after pregnancy, and with thyroid disease. Its hair signature is a diffuse thinning that does not respond to iron tablets, sometimes with alopecia areata alongside. Other signs: bloating, altered bowels, tiredness, mouth ulcers, an itchy blistering rash on elbows and knees, unexplained low ferritin or folate. Many women have no gut symptoms at all.

The test is a blood antibody (tTG-IgA), and it must be done while you are still eating gluten. Ask for it if ferritin will not rise despite tablets taken properly. On a gluten-free diet the gut heals over months and the hair follows.

Low stomach acid and acid-reducing medication

Iron and B12 need stomach acid to be absorbed. Long-term proton-pump inhibitors (omeprazole, lansoprazole) and to a lesser extent the older antacids, taken daily for reflux — very common in and after pregnancy — reduce absorption of both, and a diffuse thinning two or three years into daily use is a known consequence. Ask for a review; there are often alternatives, and B12 and ferritin should be checked.

Inflammatory bowel disease and other gut conditions

Crohn’s, ulcerative colitis, and bariatric surgery all reduce absorption and all commonly cause hair loss, both from the malabsorption and from the treatments. These are usually already diagnosed; the point is that hair loss in a woman with one of them is a nutritional problem first and needs the specialist team’s attention to iron, B12, zinc and vitamin D, not a shampoo.

What the gut-health industry gets wrong

The claim that a probiotic, a gut cleanse or a “microbiome” supplement will regrow hair has no evidence behind it. A healthy gut absorbs nutrients well, and the way to a healthy gut is fibre, variety, fermented foods if you like them, and treating any actual disease. A probiotic is harmless and may help bloating; it does not reach the follicle. Spend the money on the coeliac test.

How to tell if absorption is your problem

Ferritin under 30 that has not risen after three months of a proper iron dose, taken correctly — the method. Low B12 or folate on a normal diet. Hair loss with persistent gut symptoms. A family history of coeliac or thyroid disease. Daily antacids for more than a year. Any of those is a reason to ask for the coeliac antibody, B12, folate and a review of medication.

Where it fits

Absorption problems are a minority cause but a fixable one, and they are the reason the rule on this site is “correct what is low, then retest” rather than “take iron”. If the stores are full, the thyroid is right, and the temples and parting are still going, the follicle-level process is the reason, and that article is where to go.