Vitamin B6 (pyridoxine)
A vitamin essential for the nervous system, red-cell production and processing amino acids. Deficiency is uncommon but causes nerve and skin problems and anaemia — and, unusually, taking too much in supplements can itself damage the nerves.
What it measures
Vitamin B6 (measured in its active form, pyridoxal-5-phosphate) is a cofactor for over a hundred enzyme reactions, including making neurotransmitters, producing haemoglobin, and metabolising homocysteine (with folate and B12). A varied diet usually supplies enough, so deficiency is uncommon in isolation; when it occurs it is often alongside other B-vitamin deficiencies, in poor diet, alcohol excess, malabsorption, kidney dialysis, or with certain medications (such as isoniazid for tuberculosis). Deficiency causes nerve symptoms (tingling, numbness), a sore mouth and skin rash, a specific type of anaemia (sideroblastic), and, in severe cases, confusion. Unusually for a vitamin, B6 has a clear toxicity: taking high-dose supplements over time can cause a peripheral neuropathy — so both ends of the range matter, and a common reason to check the level is to investigate nerve symptoms in someone taking supplements.
What a high value can mean
- Over-supplementation — the commonest cause; high-dose B6 supplements taken over time.
- Vitamin B6 toxicity — can itself cause a peripheral neuropathy (tingling, numbness), which resolves when supplements stop. A high B6 is almost always from supplements, not diet.
What a low value can mean
- Poor diet or alcohol excess — often with other B-vitamin deficiencies.
- Malabsorption, kidney dialysis.
- Certain medications — isoniazid, some others, which can be given with B6 to prevent this.
- Effects — nerve symptoms, sore mouth, skin rash, sideroblastic anaemia, raised homocysteine.
When to discuss with a doctor
Vitamin B6 is not a routine test. It is worth checking in specific situations: to investigate unexplained nerve symptoms (both a deficiency and an excess can cause them — the latter increasingly seen with high-dose supplements), a sideroblastic anaemia, or a raised homocysteine, and in people at risk such as those with poor diet, alcohol excess or on certain medications. A key practical point is to review supplement use: high-dose B6 over time can cause a neuropathy that improves on stopping. Mediora.AI shows vitamin B6 alongside homocysteine and the other B vitamins so the pattern is read together; the interpretation and any supplement change belong with your doctor.