Vitamins & minerals
Folate blood test
A folate blood test measures folate (vitamin B9), a vitamin your body needs to make red blood cells and, in pregnancy, to support your baby's early development. It is usually measured alongside vitamin B12 because the two work together and their deficiencies can look alike.
- What it measures
- Folate (vitamin B9) in your blood (serum folate)
- Sample
- Venous blood sample
- Fasting
- Not required
- Also known as
- vitamin B9, serum folate, folic acid
- Included in 57 Health tests
- 5 panels, from £135
Folate reference range
Guide only| Category | Guide range |
|---|---|
| Adults (serum folate) | > 3.0 µg/L |
Serum folate reflects recent intake and fluctuates with diet; deficiency is generally considered below about 3 µg/L. Red-cell folate reflects longer-term status. µg/L is the same as ng/mL.
These are general UK adult guide ranges from public health sources, shown for orientation only. Reference ranges vary by laboratory, assay, age and sex, so your result is always interpreted against the range quoted by the analysing laboratory on your report.
What does a high folate level mean?
A high folate is rarely a problem in itself and usually reflects supplements or fortified foods.
It matters mainly because a high folate can mask an underlying vitamin B12 deficiency, which is why B12 is always checked alongside folate rather than on its own.
What does a low folate level mean?
A low folate can cause a type of anaemia (with larger-than-normal red blood cells) and symptoms such as tiredness, breathlessness and mouth ulcers.
Common causes include a low dietary intake, pregnancy (when the body needs more), heavy alcohol use, and absorption problems such as coeliac disease. In pregnancy, low folate increases the risk of neural tube defects, which is why folic acid is recommended.
When to consider a folate test
- Ongoing tiredness or suspected anaemia
- Pregnancy, or planning to conceive
- A limited or restricted diet
- Regular or heavy alcohol use
- A condition affecting absorption (e.g. coeliac disease)
- Alongside a vitamin B12 test
Frequently asked questions
This page is general information about a blood marker and is not medical advice or a diagnosis. A folate test screens and gives context; results are interpreted by a clinician alongside your symptoms, history and other markers. Always follow the guidance on your own report.