Can you take too much Vitamin B12? Overdose explained

Vitamin B12 is an essential vitamin for our body. It plays an important role in blood formation and the nervous system, for example. While the risks of vitamin B12 deficiency are widely discussed, you may also wonder whether it’s possible to take too much vitamin B12. This question is especially important for certain groups of people who frequently take vitamin B12 in the form of supplements. In this article, we explain what vitamin B12 is, how much of it is considered safe, and what happens if you take too much. 

Table of Contents

• What is vitamin B12?
• Are there significant risks associated with taking vitamin B12?
• What causes a vitamin B12 overdose?
• How can I measure my vitamin B12 level?
• What symptoms can occur with a vitamin B12 overdose?
• What can I do if I suspect an overdose?

What is vitamin B12?

Vitamin B12, also known as cobalamin, is a water-soluble vitamin that plays a crucial role in the formation of red blood cells, the functioning of the nervous system, and DNA synthesis. It naturally occurs in animal products such as fish, shellfish, meat, eggs, and dairy products but can also be added to fortified foods or taken as a dietary supplement (Cleveland Clinic, 2022).

Is vitamin B12 stored in the body?

Vitamin B12 has two important characteristics: it is both storable and water-soluble. Unlike many other water-soluble vitamins, which the body cannot store in large quantities, the body has the ability to store vitamin B12. This storage occurs primarily in the liver, and the body can often store enough vitamin B12 to last for several years. At the same time, vitamin B12 is water-soluble, which means the body can efficiently process and eliminate excess amounts through the kidneys and urine. This efficient excretion helps keep the risk of a vitamin B12 overdose relatively low, despite its storability (Havard, 2023).

What is the recommended daily intake of vitamin B12?

The recommended daily intake of vitamin B12 varies depending on age, sex, and life stage. On average, adults need about 2.4 micrograms per day. Pregnant and breastfeeding women require higher amounts (NIH, 2023). Overdose occurs less frequently with oral intake of vitamin B12 and more commonly with injectable administration (Bresoll & Daveluy, 2015).

For this reason, it is recommended that you consult your doctor before taking vitamin B12 supplements.

Are there significant risks associated with taking vitamin B12?

Vitamin B12 intake is generally considered very safe when taken in appropriate doses. However, if the recommended dose is significantly exceeded, it can lead to unpleasant side effects (NIH, 2023). This occurs less often with oral intake of vitamin B12 and more frequently with injections (Bresoll & Daveluy, 2015).

Some evidence suggests that persistently elevated plasma vitamin B12 concentrations may be associated with cancer, although more research is needed to confirm this (Urbanski et al., 2020; Obeid, 2022).

What causes a vitamin B12 overdose?

Vitamin B12 is known for its low toxicity, and as a water-soluble vitamin, it is usually efficiently excreted by the body. However, an overdose cannot be completely ruled out under certain circumstances. Excessive intake of vitamin B12 through supplements and medical treatments—especially if taken without medical advice or proper medical supervision—can pose a health risk. This is particularly true when using high-dose preparations or receiving frequent vitamin B12 injections. Special caution is advised for individuals who have altered vitamin B12 absorption due to certain medical conditions or medications, or who are individually sensitive to higher doses. Always consult a doctor before taking supplements and get tested.

How can I measure my vitamin B12 level?

Measuring your vitamin B12 level is an important step in ensuring that you are getting enough—but not too much—of this essential nutrient. This can be especially important if you notice signs of either an overdose or a deficiency. Vitamin B12 levels are typically measured through a blood test. This test measures the amount of vitamin B12 in the blood and can determine whether your B12 values are within the normal range.

Homed-IQ offers a convenient and effective way to check your vitamin B12 level, as well as other vitamins (B9 and vitamin D). With the Active Vitamin B12 Blood Test (Holo-TC) or the Vitamin Deficiency Test, you can easily perform a test at home without needing a doctor’s appointment.

What symptoms can occur with a vitamin B12 overdose?

An intake of vitamin B12 that significantly exceeds recommended levels can lead to unexpected bodily reactions. Below are the most common symptoms of a vitamin B12 overdose:

• Nausea, vomiting, diarrhea, constipation
• Anxiety, restlessness
• Headaches, dizziness
• Tingling sensation, numbness
• Skin rashes, acne, itching

Source: Kubala, 2023

These symptoms may also be caused by other health conditions. Therefore, if any of these signs occur, you should always consult a doctor to determine the exact cause (Mayo Clinic, 2023).

What can I do if I suspect an overdose?

Appropriate treatment for a vitamin B12 overdose usually involves reducing vitamin intake. A blood test can determine your individual vitamin B12 level, which serves as a basis for reducing the intake of B12 supplements or investigating other possible causes.

Summary

An overdose of vitamin B12 is rare but can occur with excessive intake. It is important not to exceed the recommended daily dose and to seek medical advice if in doubt.