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Vitamins

Holotranscobalamin Test

Holotranscobalamin measures the earliest marker of B12 deficiency. For men, early detection of B12 depletion may help preserve energy levels, cognitive sharpness, and nervous system health before symptoms develop.

Doctor's Assessment Included

When is this value abnormal?

Decision limits per result, in pmol/l
Result Value (pmol/l)
Low < 20
Borderline 20–40
Sufficient ≥ 40

Cut-off values differ between laboratories (Saltro 20/40 pmol/l; elsewhere 25/45, or 35/50 internationally). These bands follow Saltro. Active B12 is not suitable for monitoring during supplementation.

Source: Saltro

Reference ranges may vary between laboratories. When you order a test, a BIG-registered doctor assesses your personal results in context. For treatment decisions, discuss your results with your GP.

Holotranscobalamin: what this test measures

This test measures holotranscobalamin (holoTC), the complex of vitamin B12 bound to transcobalamin II. This represents roughly 10-30% of circulating B12 but is considered the only form available for cellular uptake and metabolic use.

Holotranscobalamin: why this value matters

Early B12 depletion in men may be associated with subtle declines in energy, concentration, and physical performance. Holotranscobalamin could help detect these changes early, giving you and your healthcare provider time to act before deficiency sets in.

Holotranscobalamin: how the blood test works

Referral
No GP referral needed. After the order we arrange the referral through ZorgDomein, within one business day; orders after 17:00 or at the weekend start on the next business day. ZorgDomein emails a barcode, and that barcode is what the draw site needs.
The draw
A blood draw from a vein in the arm, at a partner laboratory's draw site. No home kit, no finger prick.
Where
650+ draw sites run by independent laboratories across the Netherlands. Draw sites

Holotranscobalamin: when is testing worthwhile?

Testing may be recommended when total B12 results are borderline, if you have risk factors for B12 deficiency, or when your healthcare provider wants a more sensitive assessment of your B12 status. It can help clarify ambiguous total B12 results.

Holotranscobalamin: symptoms of a high or low value

Low Levels

Some people with low holotranscobalamin may experience early signs of B12 deficiency including subtle fatigue, mild cognitive difficulties, and slight mood changes. These symptoms may appear before more obvious signs of deficiency develop.

High Levels

Elevated holotranscobalamin levels are generally not associated with specific symptoms. However, very high levels may occasionally be seen in certain medical conditions and should be discussed with your healthcare provider for proper interpretation.

Holotranscobalamin: lifestyle and this value

Supporting healthy B12 levels through diet may include consuming animal products such as meat, fish, eggs, and dairy. Those on plant-based diets should consider discussing B12 supplementation with their healthcare provider to maintain adequate stores.

Holotranscobalamin: frequently asked questions

How is holotranscobalamin different from active B12?

Holotranscobalamin and active B12 measure the same thing — the biologically active form of vitamin B12 bound to transcobalamin II. They are essentially the same test, sometimes referred to by different names in different clinical settings.

When would my doctor order this test instead of total B12?

This test is often ordered when total B12 results are borderline or inconclusive, or when a more sensitive early detection of B12 depletion is desired. It may provide clearer information about your body's functional B12 availability.

Can holotranscobalamin detect deficiency earlier than other tests?

Holotranscobalamin is considered one of the earliest markers to change when B12 stores begin to deplete. It may detect insufficiency before total B12 levels fall below reference ranges, potentially allowing for earlier intervention.

Holotranscobalamin: sources

  1. Saltro (Unilabs). Actief vitamine B12 (holotranscobalamine): afkapwaarden. Geraadpleegd 14 juli 2026. (retrieved 2026) saltro.nl

Tests with related values

These panels measure values from the same category as this marker.

Medical reviewer

Medical standards

Dr. Naimi oversees the medical standards behind our content and assessments.

Medical policy
CIBG Ministerie van Volksgezondheid,
Welzijn en Sport Official BIG registration BIG 49928676701 Opens in a new tab

Holotranscobalamin

€49,-