Skip to content
Cart
Sampling fee?

The sample collection fee is a fixed cost that refers to the visit to the clinic where you submit your sample. The fee is not affected by how many tests you have ordered, but varies depending on the order value:

  • For order values under SEK 350, the sampling fee is SEK 129.
  • For order values between SEK 350 and SEK 1000, the fee is SEK 59.
Free sampling fee

For purchases over 1000 SEK, the sampling fee is included.

Get 10% off your first order with code TESTM10
Testmottagningen logo
en
sv
Testmottagningen logo
Search blood tests or MRI scans

Holotranscobalamin – what the test shows and how it differs from regular B12

2025-10-29

Holotranscobalamin – what the test shows and how it differs from regular B12

Holotranscobalamin (HTC) is the biologically active form of vitamin B12 — the fraction that the body can actually use. The test is performed to detect early stages of B12 deficiency and provides a more accurate picture of the body’s true vitamin status than total B12 measurements.

HTC

279 kr189 kr

Health checks for increased well-being

Read more

Contents

Quick version

What is S-holotranscobalamin?

Holotranscobalamin (HTC) is the active form of vitamin B12 found in the blood — the form that can actually be absorbed and used by the body’s cells. Vitamin B12, or cobalamin, binds to two different proteins when it circulates in the bloodstream:

  • Transcobalamin (TC) – binds about 20–30% of B12 and forms holotranscobalamin, the active form of the vitamin.
  • Haptocorrin (HC) – binds a large portion of B12, but this form is inactive and cannot be used by the cells. Much of the haptocorrin-bound B12 is eventually taken up by the liver and excreted through bile.

What is the difference between S-holotranscobalamin and total B12?

Total B12 measures both the active and inactive forms of the vitamin, while S-holotranscobalamin specifically shows the amount of active, biologically available B12 in the blood. This means that an S-holotranscobalamin test provides a more direct picture of how much functional B12 the body actually has access to. Active B12 levels tend to drop earlier than total B12, making this test more sensitive and particularly useful for detecting early B12 deficiency.

Why is S-holotranscobalamin tested?

The test is often used to confirm a suspected B12 deficiency, especially when total B12 levels are normal but symptoms suggest a deficiency. It can also be used to:

  • Identify early B12 deficiency before total levels decrease.
  • Investigate symptoms such as fatigue, dizziness, tingling, memory problems, or low mood.
  • Assess B12 status in people with impaired absorption, such as vegetarians/vegans or patients with celiac disease or inflammatory bowel disease.
  • Monitor treatment with medications that can affect absorption capacity.

When should I get tested?

An S-holotranscobalamin test may be relevant if you experience:

  • Fatigue or persistent tiredness without a clear cause
  • Tingling, numbness, or balance problems
  • Low mood, irritability, or concentration difficulties
  • Paleness, heart palpitations, or shortness of breath

Can S-holotranscobalamin indicate autism?

No, this test is not used to detect or diagnose autism. It only measures the amount of active vitamin B12. Low B12 levels can affect brain and nervous system function, but there are no direct links to neuropsychiatric conditions.

Questions and answers

Holotranscobalamin is the active form of vitamin B12 — that is, the portion that the body can actually absorb and use. It is bound to the transport protein transcobalamin, which enables the vitamin to be taken up by the cells.

Total B12 measures the overall amount of the vitamin present in the blood, including both active and inactive forms. Holotranscobalamin, on the other hand, shows only the active portion — the part that can be absorbed and used by the cells. Therefore, a holotranscobalamin test can provide a more accurate picture of your vitamin status and makes it possible to detect a B12 deficiency at an earlier stage.

This test is useful for confirming a suspected B12 deficiency even when total B12 levels appear normal. Since holotranscobalamin reflects the amount of active B12, its levels decrease before the total B12 value is affected — allowing an early-stage deficiency to be detected sooner.

The symptoms are similar to those of a vitamin B12 deficiency — for example, fatigue and reduced energy, tingling or numbness in the hands and feet, memory or concentration difficulties, pale or slightly yellowish skin, and sores in the mouth or on the tongue. The symptoms may develop gradually over time.

The reference range can vary slightly between laboratories, but the threshold for deficiency is usually around

The most common cause of low holotranscobalamin is insufficient intake of vitamin B12 through the diet — for example, in individuals who follow a vegetarian or vegan diet. Other possible causes include reduced absorption in the intestines (such as in cases of gastritis, celiac disease, or after stomach surgery), pernicious anemia, or the use of medications that affect stomach acid or nutrient absorption.

To treat low holotranscobalamin, vitamin B12 must be supplemented — either in tablet form or through injections, depending on the cause and the body’s ability to absorb it. If the deficiency is due to an underlying medical condition, lifelong treatment is often required.

No. The test only measures vitamin B12 and has no relevance for autism or other neuropsychiatric diagnoses.

Relaterade tester

-32%
S-Holotranscobalamin
  • Measures active vitamin B12
  • Detects B12 deficiency earlier than total B12
  • Used in the investigation of anemia, neurological or psychological symptoms
  • Suitable for risk groups such as the elderly, vegans, and people with impaired absorption

    • 279 kr189 kr