B12 and folate deficiency are among the most treatable causes of persistent fatigue, brain fog and pins and needles and among the most frequently missed. We measure active B12, the fraction your cells can actually use, rather than the total figure a standard test reports. Results in 24–72 hours, with an optional doctor’s review.
B12 and folate deficiency creep up slowly. Symptoms are vague enough to be attributed to stress, poor sleep or simply getting older, which is why deficiency is often present for a long time before anyone tests for it.
This panel is particularly worth considering if you:
If you have numbness, tingling or balance problems, please don’t wait on a private test result before speaking to your GP. Neurological symptoms from B12 deficiency need assessing promptly this panel supports that conversation, it doesn’t replace it.
Most of the B12 circulating in your blood is bound to a protein that cannot deliver it into your cells. Only the fraction carried on transcobalamin active B12 is actually available for your body to use. A standard total B12 test counts both, which means it can return a comfortably normal figure while the usable portion is already low. Active B12 measures the part that matters, and it tends to fall earlier than total B12, which is what makes it the more sensitive marker for picking up deficiency at a stage where it’s easily corrected.
Folate works alongside B12 in the same pathway, and the two deficiencies produce almost identical blood and symptom pictures. That similarity is precisely why they’re tested together rather than separately: correcting folate while an undetected B12 deficiency continues can resolve the anaemia while leaving the neurological effects of low B12 to progress. Testing both at once establishes which is actually low and that determines the treatment.
B12 is the one common blood test where recent supplementation genuinely changes the answer.
Otherwise there’s no special preparation. You don’t need to fast for B12 and folate.
Your report shows your active B12 and folate against their reference ranges. With a doctor’s review added, it will also explain:
Where B12 is low, identifying the cause matters as much as the number. Deficiency from a plant-based diet and deficiency from an absorption problem look identical on paper but are managed completely differently one responds to diet or tablets, the other usually needs injections for life. Your report will say which possibility your result points to, and what would confirm it.
Yes – and this is the reason B12 deficiency is missed so often.
Most people assume a blood test would have picked it up, because B12 deficiency is associated with anaemia. But the anaemia is a late feature. The neurological effects of low B12 pins and needles, numbness, poor balance, memory and concentration problems can appear while the full blood count is still entirely normal, and in some people they appear without anaemia ever developing.
Two things follow from that:
This is also why folate is measured alongside B12 rather than on its own. Folate supplementation can correct the anaemia of B12 deficiency while doing nothing for the nerves so a rising blood count can look like progress while the underlying problem continues. Testing both together avoids that trap.
Fatigue, brain fog and poor concentration also overlap almost completely with low ferritin and with an underactive thyroid. If your B12 and folate come back normal and you still feel unwell, those are the next two things worth checking.
Book your B12 and folate blood test online in under 60 seconds no GP referral needed. Prefer to speak to someone? Call our team on 0331 6300 850. We can often offer a same-day appointment subject to availability, though booking ahead is the surest way to secure your slot.
Your appointment takes about 10 minutes. One of our trained phlebotomists takes a small blood sample by standard venepuncture. There's no need to fast but do tell us if you're taking B12 or folic acid supplements, or have had a B12 injection recently, as that affects how your results should be read.
Your Vitamin B12 & Folate test results are typically returned within 24–72 hours. You'll have the option to have your results reviewed and explained by a GMC-registered UK doctor for an additional fee giving you a clear written report alongside your numerical results, not just a list of numbers.
A standard test measures total B12, which includes a large fraction bound to a protein your cells can’t draw on. Active B12 measures only the portion carried on transcobalamin the part your body can actually use. Because the active fraction tends to fall first, it picks up deficiency earlier, and it explains how someone can be told their B12 is normal while still being functionally short of it.
Where it’s safe to do so, yes ideally for a week or two beforehand. Oral B12 raises measured levels within hours of a dose, so testing while supplementing can produce a normal result that tells you nothing about your underlying status. If you’ve been prescribed B12 by a doctor, don’t stop without asking them. Test anyway and tell us you’re supplementing, and we’ll interpret the result in that light.
You can, but the result will be difficult to interpret. B12 injections raise measured levels for months, not days, so a test taken soon after a loading course mostly reflects the injection. If you’re establishing whether you still need treatment, that’s a conversation to have with the doctor who prescribed it. Call us before booking and we’ll tell you honestly whether testing now is worth your money.
Because they work in the same pathway and their deficiencies look nearly identical the same fatigue, the same appearance on a blood count. Testing one without the other risks a specific problem: correcting folate while an undetected B12 deficiency continues can resolve the anaemia while the neurological effects of low B12 carry on unchecked. Measuring both establishes which is actually low, and that determines the right treatment.
Yes. Anaemia is a late feature of B12 deficiency, not an early one. Neurological symptoms such as pins and needles, numbness, unsteadiness and poor concentration can appear while your blood count is still entirely normal, and in some people anaemia never develops at all. A normal blood count is reassuring about anaemia it isn’t the same as having had your B12 measured.
No. Pernicious anaemia is an autoimmune condition in which the stomach stops producing the protein needed to absorb B12, and confirming it requires intrinsic factor antibody testing, which isn’t in this panel. What this test does is establish whether you’re deficient which is the question that has to be answered first. If your result is low and your history suggests an absorption problem rather than a dietary one, your report will say so, and that’s the point at which further testing with your GP is appropriate.
Both are recognised causes. Long-term metformin use is associated with reduced B12 absorption, and proton pump inhibitors such as omeprazole and lansoprazole reduce the stomach acid needed to release B12 from food. Neither means you should stop your medication it means your B12 is worth checking periodically, particularly if you’ve been taking either for several years.
No. Fasting isn’t required for B12 and folate. What matters is telling us about any supplements you’re taking, not when you last ate.
Results are usually returned within 24–72 hours of your sample being taken. Your laboratory report shows active B12 and folate against their reference ranges. You can add a review by a GMC-registered UK doctor, who will explain what your results mean, whether the likely cause is dietary or absorption-related, and what to do next.
This is a fully private service and isn’t affiliated with the NHS. You don’t need a GP referral and there’s no waiting list. Your sample is processed in a UKAS ISO 15189-accredited UK laboratory, and your results are yours to share with your GP if you choose to.
