Folic acid

How it works

It is converted to tetrahydrofolate, a cofactor in single-carbon transfer reactions essential for purine and pyrimidine synthesis and therefore for DNA synthesis and normal cell division.

Prescribing in practice

• Folic acid can correct the anaemia of vitamin B12 deficiency while allowing neuropathy to progress, so vitamin B12 deficiency must be excluded or treated before giving folate for macrocytic anaemia.
• Women planning pregnancy and those at higher risk of neural tube defects require appropriate preconception and early-pregnancy folate dosing.
• It is not used as the sole treatment in pernicious anaemia where the underlying problem is B12 deficiency.

Monitoring

Monitor the haematological response with a full blood count and ensure vitamin B12 status has been assessed in macrocytic anaemia.

Counselling the patient

• Folic acid is especially important before and during early pregnancy.
• Take it regularly as advised even if you feel well.
• Tell your clinician if you are also being investigated for low vitamin B12.

Evidence & guidelines

NICE recommends folic acid before conception and in the first trimester to reduce neural tube defect risk, with higher doses for higher-risk pregnancies.