Can you have too much vitamin B12?
Quick facts: Vitamin B12 is an essential nutrient that supports various bodily processes, but more is not always better. Most adults need roughly 2.4 mcg per day, with breastfeeding or pregnant people needing slightly more. A balanceddiet can usually provide all the B12 you need, though some people may need supplements. No upper intake limit has been set for B12, as the vitamin is typically easily excreted.
Ever heard that you can have too much of a good thing? This applies to vitamin B12 as much as anything else. While low B12 levels can lead to health issues, getting too much B12 isn’t recommended either.
In this guide, we explore how much vitamin B12 you need per day, how supplements may support this and what can happen if you consume too much B12 regularly.
How much vitamin B12 do you need per day?
As with other nutrients, the exact amount of vitamin B12 you need each day varies from person to person according to age, life stage and physiological needs. According to general nutritional guidelines, the recommended daily intake is:
- Adults (men and women): around 2.4 micrograms per day
- Pregnant individuals: around 2.6 micrograms per day
- Breastfeeding individuals: around 2.8 micrograms per day
- Children: ranging from approximately 0.4 to 2.4 micrograms depending on age.
These amounts are relatively small compared to some other nutrients, which means it’s relatively rare for most people to experience a vitamin B12 deficiency. However, B12 is predominantly found in animal products, so you may be at higher risk if you’re vegan or vegetarian.
In some cases, people experience B12 deficiency even when they’re consuming enough B12 on the face of things. This can be linked to an absorption issue that prevents them from using the B12 they get in their diet.
How much vitamin B12 should I take?
As mentioned, most people can meet their vitamin B12 needs through a balanced diet and don’t need supplements. Good sources of vitamin B12 include:
- Salmon
- Eggs
- Milk
- Yoghurt
- Beef
- Fortified breakfast cereals.
Since you only need a very small amount of vitamin B12, it’s really easy to get enough through your food. For example, 250 ml of milk contains roughly 1.3 mcg of vitamin B12 – over 50% of your daily requirement.
If you think you need supplements due to a restrictive diet or absorption issues, speak to a doctor first. They can let you know what an appropriate dose is based on how low your existing B12 levels are.
Fortunately, supplement doses vary widely to accommodate different levels of need. Sometimes B12 is included with other nutrients such as the other B vitamins – in which case, doses are usually on the modest side of around 20 to 100 micrograms.
If you need a stronger dose, you may be advised to try a standalone B12 supplement, which may contain as much as 1,000 micrograms to provide a targeted boost and avoid deficiency.
Tempting though it may be, it’s best not to opt for a higher dose unless advised to by a doctor. This is because the higher the dose, the greater the chance that you could experience side effects.
Can you overdose on vitamin B12?
Vitamin B12 is a water-soluble vitamin, but unlike many other water-soluble vitamins, the body can store substantial amounts of it, primarily in the liver. Any excess that cannot be absorbed or stored is typically excreted, which is one reason why vitamin B12 toxicity is considered rare.
Because of this, no official upper intake limit has been established – as it’s incredibly rare to suffer B12 toxicity.
This means you don’t need to worry if you realise you’ve taken a supplement when your diet is providing enough B12, because your body can usually handle it. However, regularly taking very high supplemental doses on top of getting enough in your diet could cause side effects. These may include:
- Digestive discomfort
- Headaches
Skin reactions.
Again, taking higher doses of vitamin B12 doesn’t carry any benefits – because higher levels will just be excreted if they’re not needed.
As with any supplement, you should follow the advice on the product label and consult a healthcare professional with any questions you may have.
Conclusion
Vitamin B12 is an essential nutrient, but as with many nutrients, balance is key. Most people don’t need supplements, and excessive intake is unlikely to benefit you beyond reaching your daily intake.
The most important thing is to maintain a healthy, balanced diet with a variety of essential nutrients. If you have health concerns you think could stem from low B12, speak to a medical professional for advice and assistance.
FAQs
What is vitamin B12 good for?
Vitamin B12 plays several essential roles in the body, making it an important nutrient for overall health. It:
- Contributes to normal energy-yielding metabolism
- Helps to support the formation of red blood cells
- Is involved in the maintenance of the nervous system
- Plays a role in DNA synthesis, which is essential for cell division and growth.
Although often associated with energy, vitamin B12 doesn’t act as a stimulant like caffeine. Instead, it helps your body to convert food into usable energy as part of normal metabolic function. Is iron vitamin B12?
No, iron and vitamin B12 are completely different nutrients, although both are important for red blood cell production:
- Iron is a mineral that’s a key component of haemoglobin, the protein that binds to oxygen for transport around the body.
- B12 is a vitamin that supports the DNA synthesis and cell division needed to produce healthy red blood cells, which carry haemoglobin in the bloodstream.
A deficiency in either nutrient can lead to anaemia, but the causes and treatments are different. Iron deficiency anaemia is typically related to low iron intake or blood loss, whereas B12 deficiency is often linked to absorption issues or dietary restrictions.
How can I get vitamin B12?
Vitamin B12 is naturally found in animal-based foods such as meat, poultry, fish, eggs and dairy products. For example, salmon, beef, eggs, milk and cheese are all good dietary sources.
For those who don’t consume animal products, such as vegans, vitamin B12 can be found in fortified foods or supplements. In some cases, supplementation may also be recommended for older adults or those with absorption issues.
If you’re worried you might be deficient in vitamin B12, speak to a healthcare professional for testing and personalised guidance.
References
National Institutes of Health Office of Dietary Supplements. (2023). Vitamin B12 fact sheet for health professionals. https://ods.od.nih.gov/factsheets/VitaminB12-HealthProfessional/
Harvard T.H. Chan School of Public Health. (2024). Vitamin B12. https://www.hsph.harvard.edu/nutritionsource/vitamin-b12/
World Health Organization. (2023). Micronutrients: Vitamins and minerals. https://www.who.int/news-room/fact-sheets/detail/micronutrients
