Vitamins and nutrition . Patient guide
Folate (Serum folate)
Also known as: Vitamin B9, Folic acid (synthetic form)
What is Serum folate
Folate is a B-vitamin essential for red blood cell formation, DNA synthesis, and the methylation cycle. It is almost always tested together with vitamin B12 because the two work as a pair and either deficiency can cause the same picture of macrocytic anaemia and fatigue.
This biomarker entry is being clinically reviewed by our team. The factual content draws on UK guidance (NICE, NHS, Royal Colleges and the relevant speciality society where cited).
Reference range
Reported in nmol/L (also seen as ng/mL (divide nmol/L by 2.266)). Final reports always carry the issuing laboratory's range, which is what your clinician will interpret against.
| Group | Range | Note |
|---|---|---|
| Adequate (NICE) | over 7 | nmol/L |
| Borderline / deficient | 3 to 7 | |
| Deficient | under 3 | |
| Often targeted clinically | over 15 | expert opinion, not a NICE threshold |
What it is
Folate is the natural form of vitamin B9 found in leafy greens, legumes, and liver. Folic acid is the synthetic supplement form. Both convert through methylenetetrahydrofolate to the active form 5-MTHF, which donates methyl groups in the synthesis of DNA, neurotransmitters, and the breakdown of homocysteine. Folate stores last only weeks, much shorter than B12 stores which last years.
Why a clinician would order it
Folate is requested alongside B12 in the work-up of fatigue, hair shedding, sore tongue or mouth ulcers, breathlessness, mood symptoms, pre-conception planning, recurrent miscarriage, and any macrocytic anaemia seen on a full blood count. Pre-conception and early pregnancy testing matters because folate deficiency increases the risk of neural tube defects.
If your level is outside the range
Symptoms of low Serum folate
- Fatigue
- Hair shedding
- Mouth ulcers and sore tongue (glossitis)
- Breathlessness on exertion
- Pale skin
- Low mood, irritability
What low can indicate. Inadequate dietary intake (most common UK cause), pregnancy and breastfeeding (demand rises sharply), coeliac disease and other malabsorption, alcohol excess, methotrexate or other antifolate medication, anticonvulsants.
Symptoms of high Serum folate
- No clinical symptoms of high folate
- Can mask underlying B12 deficiency on FBC (the anaemia improves but neurological B12 damage continues)
What high can indicate. High dose folic acid supplementation. Not clinically harmful on its own but can mask a coexisting B12 deficiency by normalising the FBC while the neurological damage progresses. Always test B12 alongside folate before supplementing.
Testing tips
Fasting preferred but not essential. Hold high-dose folic acid or folate supplements (over 200 micrograms daily), and any B-complex or multivitamin containing folate, for 24 to 72 hours before testing. Recent supplementation can mask a true deficiency by normalising the serum folate reading. Always test B12 at the same time (and hold B12 supplements for several weeks, since serum B12 stays elevated much longer than serum folate). In women planning pregnancy, the recommendation is to start 400 micrograms daily folic acid before conception and continue through the first trimester.
Where you can get this tested
Folate is included in the following WMG Health panels. Same-day appointments at our Harley Street clinic, with results clinician-reviewed.
Want a specific combination of markers we do not have a panel for? Build a custom panel and our clinicians will design one for you.
Symptoms often investigated with Folate
Folate is commonly tested when patients present with the following symptoms. If any of these resonate with you, the linked guides explain what to look for and which test pathway is appropriate.
Read this marker alongside another
Folate is most useful when interpreted together with the markers below. Each guide walks through the 4-quadrant matrix our clinicians use when both come back at once.
Sources
UK guidance our clinicians use when interpreting this marker.
This page is general patient information, not personal medical advice. A GMC-registered clinician will review your results and tailor any interpretation to you. See our Editorial Policy for how we write and review content.
Common questions about Serum folate
What is a normal Serum folate range?
Adequate (NICE): over 7 (nmol/L). Borderline / deficient: 3 to 7. Deficient: under 3. Often targeted clinically: over 15 (expert opinion, not a NICE threshold). Always interpret your own results against the laboratory range printed on your report, since assay-specific reference ranges vary.
What does a low Serum folate result mean?
Inadequate dietary intake (most common UK cause), pregnancy and breastfeeding (demand rises sharply), coeliac disease and other malabsorption, alcohol excess, methotrexate or other antifolate medication, anticonvulsants.
What does a high Serum folate result mean?
High dose folic acid supplementation. Not clinically harmful on its own but can mask a coexisting B12 deficiency by normalising the FBC while the neurological damage progresses. Always test B12 alongside folate before supplementing.
Do I need to fast or prepare for the Serum folate blood test?
Fasting preferred but not essential. Hold high-dose folic acid or folate supplements (over 200 micrograms daily), and any B-complex or multivitamin containing folate, for 24 to 72 hours before testing. Recent supplementation can mask a true deficiency by normalising the serum folate reading. Always test B12 at the same time (and hold B12 supplements for several weeks, since serum B12 stays elevated much longer than serum folate). In women planning pregnancy, the recommendation is to start 400 micrograms daily folic acid before conception and continue through the first trimester.
Can I order a Serum folate blood test privately in London?
Yes. WMG Health offers Serum folate as part of bespoke panels and several pre-built panels at our 134 Harley Street clinic. Results are clinician-reviewed by a GMC-registered doctor within 4 hours for the most common assays. Bespoke panels from £180; bookings via /contact/ or 020 3239 3378.