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Vitamins

Holotranscobalamin Test

Holotranscobalamin measures the earliest marker of B12 depletion. For women, early detection may be particularly valuable as B12 status can influence hormonal health, energy levels, and reproductive wellbeing.

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

Afkapwaarden verschillen per laboratorium (Saltro 20/40 pmol/l; elders 25/45 of internationaal 35/50). Deze banden volgen Saltro. Actief B12 is ongeschikt als controle tijdens suppletie.

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

Women may be particularly susceptible to B12 depletion during hormonal changes, pregnancy, or when using certain contraceptives. Holotranscobalamin could help identify declining B12 stores early, supporting proactive management with your healthcare provider.

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.

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Tests with related values

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

Fertility & Pregnancy

IVF Blood Test Complete (Women)

Everything in the IVF panel plus full thyroid, preconception nutrients, progesterone and CMV immunity.

TSH (Thyroid Stimulating Hormone) Prolactin AMH (Anti-Müllerian Hormone) Estradiol (E2) FSH (Follicle Stimulating Hormone) LH (Luteinizing Hormone) Free T4 (Thyroxine) Folate (Folic Acid) Vitamin B12 Ferritin Progesterone Vitamin D (25-OH) Chlamydia IgG HIV 1/2 Antibody + p24 Antigen Syphilis Screening Blood Type + Rh TPO Antibodies CMV IgG Hepatitis B Core Antibody Hepatitis B Surface Antigen Hepatitis C Antibody Rubella IgG Toxoplasmosis IgG Varicella Zoster D-Dimer Basic Blood Count
€495,-

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Holotranscobalamin

€49,-