<img height="1" width="1" alt="" style="display:none" src="https://www.facebook.com/tr?ev=6048136207047&amp;cd[value]=0.01&amp;cd[currency]=USD&amp;noscript=1"> How long should you stop supplementation for a blood test?
Aug. 16, 2023
3 min. reading time

How long should you stop supplementation for a blood test?

Question from Helen: I am interested in the test for vitamin B1/thiamine and vitamin E. Well I know that with vitamin B12, taking supplements has a huge impact on your blood value and it gets so high that it is of little use. How long should I stop supplementing for an objective reading?

A: You always measure the vitamin including the swallowed,

So it's up to you to measure your natural level, or the level including absorption by supplements.

The length of time supplements remain measurable in the blood or urine can vary based on several factors, including the specific vitamin or mineral, dosage and individual metabolism rate. In general, water-soluble vitamins are excreted from the body sooner than fat-soluble vitamins.

Here is a general overview of some common vitamins and minerals, along with an approximate period of supplementation before you can take a more objective measurement:

Water-soluble vitamins:

Vitamin C: Supplementation can be excreted quickly. You could expect a reliable reading after about 24-48 hours.

Vitamin B complex (e.g., B6, B12, folic acid): B vitamins are also excreted relatively quickly. A break of 2-7 days may be sufficient for an accurate reading.

The general advice is to stop taking B12 supplements for at least a week to a month before having a blood test. This is because supplements can raise B12 levels in the blood, masking a deficiency.

However, the exact time may vary depending on several factors, such as;

  1. the dose of the supplement, is it in a multi-vitamin , do you swallow it separately, or do you use injections
  2. duration of use,
  3. and your personal health situation.

It is important to discuss this with your doctor before you stop taking supplements, especially if you are taking them for medical reasons. Your doctor can give the best advice based on your specific situation and may also consider other factors that may affect the B12 test.

To really do 0 measurement for vitamin B12 is at high dosage 3 months , but it is not advisable to stop suplletie because langduring B12 deficiency can lead to permanent damage.

So it is very important that before treatment starts, the cause of B12 deficiency is properly identified. with tests such as b12serum, holotc, methylmalonic acid and homocysteine

Biotin (vitamin B7): Approximately 24-48 hours.

Fat-soluble vitamins:

Vitamin A: Fat-soluble vitamins can stay in the body longer. It may take several weeks to months for levels to stabilize.

Vitamin D: Also fat-soluble. Depending on dosage and degree of sunlight exposure, supplementation effects may take several weeks to months to disappear.

Vitamin E: Fat soluble. Several weeks to months.

Vitamin K: Fat soluble. Several weeks to months.


Iron: Depending on dosage and individual iron status, it may take several weeks to months for the effect of supplementation to fade.

Zinc: A few days to a week.

Magnesium: Several days to a week.

These estimates are general and may vary from individual to individual. If you plan to get an objective measurement, it is advisable to consult with your thrapeut before you stop taking supplements. They can guide you based on your specific situation and health condition.

Food is an ongoing source of vitamins and minerals, so following a balanced diet is essential for optimal health

Testing your blood levels after supplementation can have several reasons and can be helpful in understanding your health and nutritional status. Here are some possible reasons why you might choose to have your blood levels tested after taking nutritional supplements:

  1. If you suspect a deficiency in certain vitamins or minerals, supplementation can be used to make up the deficiency. Testing your blood levels after supplementation can help determine if the supplementation has been effective in raising your levels.
  2. Optimizing supplementation: Testing your blood levels can help determine the proper dosage of supplements. This is especially important with fat-soluble vitamins such as vitamin D, where too much supplementation can lead to toxicity.
  3. Individual variability: People have different needs when it comes to nutrients. Testing your blood levels can help identify individual variations and adjust supplementation accordingly.
  4. Supporting health goals: If you have specific health goals, such as strengthening your immune system, improving bone health or reducing fatigue, testing blood levels can help assess the effectiveness of your supplementation in achieving those goals.
  5. Medical conditions: Some medical conditions or medications can affect the absorption or metabolism of certain nutrients. Testing blood levels can help monitor the impact of these factors.
  6. Ensure the health of certain populations: In some cases, such as pregnancy, blood tests after supplementation can help ensure that sufficient nutrients are available to both the mother and the developing fetus.

About the author
Ellen is the founder of Blood Values Test. She gained her experience with health examinations for companies, schools and government institutions at HumanCapitalCare arbo- en gezondheidsdienst. In 2009 she became director of Diagnostics Netherlands, a collaboration between all major general practitioners laboratories in the Netherlands. At the U- Diagnostics laboratory in Utrecht, she was responsible for blood testing at GP surgeries. Until she founded Blood Values Test for individuals in 2013.
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