Prevention and treatment of iron and folate deficiency anaemia, most often during pregnancy and breastfeeding, and in people whose diet or absorption leaves both nutrients low.

Iron supplies the core of haemoglobin, which carries oxygen. Folic acid is needed to make the DNA of each new red blood cell, so without it the marrow produces fewer, larger and less useful cells. Supplying both lets the marrow make the right number of properly filled cells. In pregnancy, folic acid also supports the closure of the baby's neural tube in the earliest weeks.

Dark stools, constipation, nausea and stomach discomfort from the iron; folic acid itself is usually well tolerated.

Folic acid can mask a vitamin B12 deficiency while nerve damage quietly continues, so B12 should be checked if deficiency is suspected. Do not take extra iron on top of this without advice, keep it away from children, and separate it from tea, milk, antacids and thyroid medicines by at least two hours. The dose of folic acid in pregnancy should be the one your doctor advises, which is higher in some situations.