Lab marker
Folate
Vitamin B9 · Folic acid (synthetic) · Serum folate
Essential for DNA synthesis and methylation — almost universally repleted in fortified-food countries but still measured in unexplained anaemia or pregnancy planning.
What it measures
Serum folate concentration. Reflects recent dietary intake (within days). Red cell folate, less commonly measured, reflects average intake over the preceding ~3 months and is the more stable status indicator.
Reference context
3 guideline sources
Recent intake (or a single folate-rich meal) elevates serum folate within hours and can mask longer-term deficiency. Red cell folate is more reliable for status. In fortified-food countries, true dietary folate deficiency is now uncommon outside specific clinical groups (alcohol-use disorder, malabsorption, methotrexate use, pregnancy without supplementation).
Population context — consult guideline targets below
Mechanism
Why moving this marker matters
Folate (B9) is a methyl donor in DNA synthesis and homocysteine remethylation. Deficiency causes megaloblastic anaemia (indistinguishable haematologically from B12 deficiency), elevated homocysteine, and — most consequentially — neural tube defects in pregnancy. Mandatory food fortification (introduced in many countries from the late 1990s onward) has substantially reduced clinical deficiency.
Guideline targets
What major guidelines recommend
BCSH 2014 (deficient, serum)
<7 nmol/L (<3 ng/mL)
BCSH 2014 (borderline, serum)
7–10 nmol/L
WHO 2015 (red cell folate for NTD prevention)
>906 nmol/L in women of reproductive age
How to measure
The test, where to get it, when to repeat
Method
Standard blood draw for serum folate. Red cell folate (RBC folate) requires a separate assay and reflects longer-term status.
Where
GP request or comprehensive private panel.
Typical cost
€10–25 private.
Fasting
Not required
When to test
BCSH 2014
Measure alongside B12 when investigating macrocytic anaemia, unexplained symptoms, or pre-pregnancy planning.
Where to test
Independent labs offering this test
Healicus refers you to independent laboratories. You order from the lab; they take the sample, run it, and return your result on their own platform. Healicus never sees your value.
Randox Health
UK · EU · INTLClinic-based premium panels — wider biomarker breadth than home-test brands.
Visit Randox Health
Synlab
DE · EU · INTLEurope-wide medical lab network — referrals via partner GPs and direct-to-consumer programmes where offered.
Visit Synlab
Cerascreen
DE · EUEstablished German home-test catalogue — ISO-certified labs, German-language reports.
Visit Cerascreen
Medichecks
UKUKAS-accredited home blood-test panels with GP-equivalent biomarker coverage.
Visit Medichecks
Healicus is not the provider. Your contract for the service is with whoever you choose. Links labelled Sponsored are paid affiliate relationships; unlabelled links are editorial reference only. See our disclosure for the full policy.
Context
Reading the numbers
Recent intake (or a single folate-rich meal) elevates serum folate within hours and can mask longer-term deficiency. Red cell folate is more reliable for status. In fortified-food countries, true dietary folate deficiency is now uncommon outside specific clinical groups (alcohol-use disorder, malabsorption, methotrexate use, pregnancy without supplementation).
Caveats
Folate supplementation can mask the haematological signs of B12 deficiency while the neurological damage progresses. Always check B12 when supplementing folate, especially in older adults.
Practices
What's been shown to influence this marker
Leafy greens, legumes, citrus, and whole grains in the Mediterranean pattern provide ample dietary folate; adherent adults reliably maintain replete status.
Heavy alcohol intake impairs folate absorption and accelerates depletion. Reduction reverses this within weeks.
Mediterranean dietary pattern
Habit·Olive oil, fish, nuts, legumes, plants. The most-studied diet for cardiovascular and cognitive longevity.
Why
The Mediterranean pattern — heavy on plants, olive oil, fish, nuts, legumes; moderate fish and dairy; light on red meat — has the strongest evidence base of any specific diet for long-term cardiovascular and cognitive outcomes. PREDIMED, the largest trial, showed ~30% reduction in major cardiovascular events vs. low-fat control.
Slot in your day
How to do it
How
Olive oil as the primary fat. Plants at every meal. Fish 2–3× per week. Nuts daily (small handful). Red meat once a week or less. Wine optional, with food.
Sticking with it
Stock the kitchen for one week's pattern. Decisions live in the shopping list, not at mealtime.
Markers this may influence
Evidence
30g fiber/day
Habit·Most adults eat half what they need. Strong dose-response with all-cause mortality.
Why
Fiber feeds gut microbiota, slows glucose absorption, supports cardiovascular health, and predicts mortality independent of other dietary factors. Most adults consume 12–15g/day; the target for cardiovascular benefit is 25–30g+. Whole foods (legumes, vegetables, oats, berries) are better sources than supplements.
Slot in your day
How to do it
How
Add a serving of beans/lentils most days. Berries with breakfast. Vegetables at lunch and dinner. Tracked once for a week, the gap to 30g becomes obvious.
Evidence
Limit alcohol intake
Habit·Lancet pooled analysis (n=599,912): lowest mortality risk threshold is ~100 g/week — about 5-6 standard drinks total.
Why
Wood et al. 2018 Lancet combined individual-participant data from 83 prospective studies (n=599,912 current drinkers in 19 high-income countries). Above ~100 g/week (about 5-6 UK standard units), all-cause mortality climbs in a dose-response manner. Below that threshold the curve is roughly flat — there is no protective effect. Reductions from heavier intake to ≤100 g/week could add up to 2 years of life expectancy at age 40.
How to do it
How
Track intake honestly for one week. If above threshold, set a weekly cap rather than a daily one (avoids the 'I'll catch up' trap). Several alcohol-free days per week is the simplest pattern. Sleep quality typically improves within 1-2 weeks of reduced intake.
Ideal for
Anyone currently drinking above ~100 g/week (≈one bottle of wine, six pints of beer, or a half-bottle of spirits).
Markers this may influence
Evidence
See also
Related markers
Take to your physician
Worth discussing
- Whether to test red cell folate when serum is borderline.
- If pregnancy is planned, ensuring 400 µg/day folic acid for at least 1 month preconception (higher doses in women on antiepileptics, with prior NTD-affected pregnancy, or with raised BMI).
- Whether your medications (methotrexate, sulfasalazine, antiepileptics) require folate monitoring or supplementation.
Sources
Cited literature
- [1]Devalia et al., BCSH — Guidelines for the diagnosis and treatment of cobalamin and folate disorders (Br J Haematol)(2014)
- [2]WHO — Serum and red blood cell folate concentrations for assessing folate status in populations(2015)
- [3]Halsted CH, Alcohol and folate interactions: clinical implications (Semin Liver Dis)(2002)
Edited by Carl Pöhl, MD · Healicus editorial
Last reviewed May 2026
Keep reading