Health Reference LibraryFolate deficiency: symptoms, levels and what to do (UK)
This entry is part of the Nutri Tailor Health Reference Library — cited research on supplements, nutrients and adjacent areas of health.
Summary
Folate deficiency is read from serum folate: below 3 micrograms per litre (7 nmol/L) is deficient, 3 to 4 is borderline, and 5 to 20 is adequate. The symptoms overlap with B12 deficiency: tiredness, low mood, mouth ulcers, a sore tongue and, in severe cases, megaloblastic anaemia. The one rule UK guidance is firm on is that B12 is checked before folate is corrected, because folate can improve the blood picture while nerve damage from a B12 problem continues. Pregnancy is the special case: 400 micrograms of folic acid a day from before conception to twelve weeks, higher on GP advice.
How it works
Folate is needed to make DNA, so the fastest-dividing cells feel its absence first: red blood cells become large and fewer (megaloblastic anaemia), and the lining of the mouth and gut suffers, which is why mouth ulcers and a sore tongue are early signs. Stores last only a few months, so a poor diet, alcohol or an absorption problem shows in the blood quickly. Folate and B12 work in the same pathway, which is why the two are read together.
Special populations
Low intake of leafy greens, beans and fortified foods; alcohol; coeliac and other absorption conditions; and some prescribed treatments, which is a GP conversation. Pregnancy is the special case: 400 micrograms of folic acid a day from before conception to twelve weeks, higher on GP advice.
Guideline positions
Serum folate is reported in micrograms per litre or nanomoles per litre, and the number differs by a factor of about 2.3, so check the unit before reading it. Below 3 micrograms per litre (7 nmol/L) is deficient, covered in folate below 3. 3 to 4 is borderline, covered in folate 3 to 4. 5 to 20 is adequate, covered in folate 5 to 20. Red cell folate reflects the longer-term picture where it is tested. UK guidance checks B12 before correcting folate at any of these levels.
Practical framework
Read the number with the free blood test result interpreter, alongside B12; the B12 deficiency guide explains why the two are read together. Correct folate once B12 is known, choosing between the forms in folate vs folic acid vs methylfolate. Retest at eight to twelve weeks. Nutri Tailor stocks folate as methylfolate.
Sources
- 2024. Folate Deficiency. Patient.info Professional.
- 2026. Folate Deficiency. Merck Manual Professional.