Specialist marker · Vitamins
An active B12 test measures holotranscobalamin, the share of vitamin B12 your cells can actually take up. It can pick up an early deficiency that a standard total B12 test misses. You can add it to TrueVitals Ultimate for £59, or get it included in Signature (£799).
Add-ons are tested on the same blood draw as your panel and reported inside your clinician-reviewed report, read alongside your other 140 results. They are not sold on their own.
Pay in instalments with Klarna or Clearpay at checkout. Want it with Advanced instead? Email support@truevitals.co.uk and we will set it up.
A standard B12 test measures all the B12 in your blood, but most of it is bound to a carrier protein your cells cannot use. Only the portion bound to transcobalamin, called holotranscobalamin or active B12, is delivered into cells.
Active B12 tends to fall first when you start running short, so a total B12 in the lower part of the range can hide a real shortfall. Ultimate already includes total B12, folate and red cell size (MCV); active B12 settles the question when total B12 is borderline.
Many UK labs treat active B12 below about 25 to 35 pmol/L as deficient and up to about 70 pmol/L as a grey zone where deficiency is possible. Exact cut-offs vary by lab, and your report uses the lab's own range.
| Option | Includes it | Price | What else you get |
|---|---|---|---|
| Ultimate + active B12 add-on | Yes | £458 incl. clinic draw (home visit £487) | Read alongside total B12, folate, MCV, RDW and ferritin. Clinician-reviewed report in 4 working days. |
| TrueVitals Signature | Yes | £799 incl. draw | Included as standard with red cell folate and homocysteine. Up to 12 working days. |
| TrueVitals Advanced | On request | £319 + £59 | Can be added on request by email. |
| NHS GP | On request | Free if clinically indicated | Some NHS labs add it automatically when total B12 is borderline. |
TrueVitals prices checked 5 November 2026. Every TrueVitals report is clinician-reviewed. Pay in instalments with Klarna or Clearpay. Book a draw at one of 103 partner clinics, or add a home visit.
When to see your GP: numbness, tingling, balance problems or a sore red tongue alongside low B12 need medical review, as some causes (such as pernicious anaemia) need injections rather than tablets.
A private panel is a good way to get a baseline, understand a result in context and track it over time. It does not replace your GP for symptoms, and anything that needs follow-up is flagged in plain words in your report.
Active B12 on its own rarely tells the whole story. In TrueVitals panels it is reported with these related markers:
It is more specific. Total B12 includes B12 your cells can't use; active B12 measures the part they can. It is most useful when total B12 is in the lower part of the range.
Ultimate includes total B12, folate and red cell indices. Active B12 is a £59 add-on, and is included in Signature.
If you want to see your natural status, stop B12 supplements for about a week first. If you want to check supplements are working, keep taking them as normal.
Usually low intake or reduced absorption. Your report reads it with homocysteine, MCV and folate, and suggests next steps.
Yes. Ultimate + active B12 with a home visit is £487.
How this page was written: by James Smillie, founder of TrueVitals, reviewed by the TrueVitals clinical review team, using NHS and laboratory reference sources. Ranges are typical values; your report uses your lab's own ranges. TrueVitals sells the panels named on this page, so we have stated plainly what this test cannot do. Last updated 5 November 2026.
Ultimate + active B12: £458 including the clinic draw, or Signature with active B12 included: £799.
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