Holo‑TC; sensitive B12 marker.
Blood collection at collection point
After your order you receive instructions by email
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Blood collection at 1,000+ locations across the Netherlands
Holotranscobalamin (HOLO-TC) is a biomarker that measures the amount of vitamin B12 in the body that is directly available for cellular uptake. It is an early indicator of vitamin B12 deficiency, as it only reflects the portion of vitamin B12 that can be actively used by the body.
Testing HOLO-TC is useful for people experiencing symptoms that may indicate a vitamin B12 deficiency, such as fatigue, weakness, memory problems, or neurological changes. It is also valuable for individuals at risk of vitamin B12 deficiency, such as the elderly, vegans, and people with certain stomach conditions or who use specific medications.
HOLO-TC levels indicate the amount of immediately available vitamin B12 in the blood. This helps determine whether the body has sufficient vitamin B12 for essential functions such as DNA synthesis, blood cell production, and nerve maintenance.
A high level of HOLO-TC is generally uncommon and is less frequently associated with health problems. However, in rare cases, it can indicate certain medical conditions or the use of vitamin B12 supplements.
A low level of HOLO-TC indicates a deficiency of available vitamin B12 in the body. This can lead to various health problems, including anemia, nerve damage, fatigue, and cognitive impairments.
Answers to what people usually want to know.
After ordering we generate a referral letter and email you the instructions. You pick a collection point yourself and book an appointment there. Blood is drawn at the location, processed at the lab, and your result arrives digitally.
Often within a few working days. How soon you can be seen depends on how busy the location is and the type of analysis. For specialist analyses we first ship collection materials, which takes a bit longer.
At most collection points yes. Some accept walk-ins. This is clearly indicated per location. You choose the location that works best for you.
That depends on the test. Whether fasting is required, and from what time, is clearly stated in the instructions you receive after ordering. No surprises at the counter.
It varies per analysis: from same-day to a few working days. Standard values often come back quickly; analyses that go to an external lab can take a bit longer. You get an email with a link to your digital result, including a short explanation per value.
We work with 1,000+ collection points across the Netherlands. After ordering you'll see which locations near you are available and you pick where you'd like to go.
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This test is included in Dutch healthcare guidelines and is regularly used for its respective indications.
Rationale for this test
Holotranscobalamine (holo-TC) is een gevalideerde biomarker voor vitamine B12-status die in de Nederlandse reguliere zorg wordt gebruikt. De test meet het direct beschikbare vitamine B12 en is een vroege indicator van tekort. De klinische betekenis is goed onderbouwd in zowel Nederlandse als internationale richtlijnen voor diagnostiek van vitamine B12-deficiëntie.
Last reviewed on
Dutch clinical guidelines and healthcare organisations
International scientific literature
We recommend consulting these independent sources before ordering a preventive health check.
Brochure on preventive health checks: careful choice, reliability, pros and cons, checklist.
Independent information about preventive health checks from the National Institute for Public Health and the Environment.
Reliable patient information about illnesses and complaints from Dutch GPs (NHG).
Public-facing website of the Dutch Society for Clinical Chemistry with explanations of blood tests and laboratory values.