B12 is hands down one of the most commonly consumed vitamin supplements.
Not only is it one of the best-selling single-ingredient supplements in the world, but it is also used in all kinds of different pre-made supplement stacks. Protein powders, weight gainers, pre-workouts, fat burners, nootropics, energy supplements – all of these supplements regularly list B12 as an ingredient.
More than that; they usually include MASSIVE quantities of B12.
It is not unusual for a B12 supplement to provide thousands of times your recommended daily intake (RDI) per serving.
The standard B12 stacks sold in Holland & Barret or GNC start at around 400% of your RDI. The mid-range products deliver 4,000% of your RDI of B12, while the more powerful ones give you 40,000%!
When a substance starts getting dosed at 400 times your recommended daily dose, you do need to stop and ask yourself – is this necessary? Or more importantly, is it safe?
Is it dangerous to be taking so much B12 daily?
Can B12 cause side effects in large doses?
Are there any long-term health risks?
Let’s take a quick look at the scientific literature on B12 to see if we can find any cause for concern. Below you will find a breakdown of what B12 does in the body, why people take it, and what the known dangers are. In the end, we’ll tell you whether or not we think it’s dangerous to take too much B12.
WHAT DOES B12 DO?
B12 is one of those micronutrients which seems to be involved in countless different reactions, processes, and functions in the human body.
B12 is necessary for the healthy formation of red blood cells. It helps synthesize DNA, and it is necessary for the proper functioning of the nervous system. Yes, that includes the brain; without B12, the nerve cells in your brain cannot function properly. As a result, your brain can’t function properly.
But the main thing that B12 is known for is energy metabolism.
B12 is needed for the metabolism of energy from food. Every single cell in your body needs B12 to be able to release energy from fatty acids.
This is why B12 is used in many sports supplements (such as fat burners or pre-workouts) – to enhance energy metabolism from food and thereby improve athletic performance.
Yes, B12 deficiencies are definitely a real thing.
They are extremely rare, but they do occur.
This might sound obvious, but in the case of many vitamins there is actually no clinical definition of deficiency – they just don’t happen. But B12 deficiencies do occur, and they can take some time to rectify.
The symptoms of B12 deficiency include:
- Pale skin
- Blurry vision
- Loss of appetite
- Muscle tingling
- Muscle numbness
If a B12 deficiency is left untreated for a prolonged period of time, the adverse effects can become much more serious.
People at higher risk of B12 deficiency include older people, people who don’t eat any animal products, people who don’t consume any B12-fortified foods, people suffering from digestive diseases, and people with an inability to absorb B vitamins properly.
A B12 deficiency is usually pretty easy to spot. However fixing a B12 deficiency can be a difficult, lengthy process.
You usually need time for your B12 stores in your liver to be replenished before all of your symptoms will go away completely. Until you have replenished your body’s B12 stores, you should be in the clear for a long time – your B12 stores can take 3-5 years to completely exhaust!
The easiest way to rectify a B12 deficiency is to use a potent B12 supplement.
This is usually why people take the 40,000% RDI stacks – they’re trying to quickly fix a serious nutritional deficiency.
But what about otherwise healthy people?
Is it safe to take such large amounts of B12?
Might taking too much B12 daily be dangerous?
Let’s look at the studies.
IS TOO MUCH B12 DANGEROUS? – WHAT THE STUDIES SAY
First of all, we need to say that no tolerable upper intake level (UL) has been established for Vitamin B12.
The tolerable UL is the amount of a given substance that can be consumed without significantly raising the risks of side effects.
B12 does not have a tolerable UL – as far as medical science is concerned, it can be consumed in practically any quantity without posing serious side effect risks.
Many clinical trials looking at the efficacy of B12 supplements have used 2,000 micrograms per day. That is roughly 80,000% of your RDI of B12. Even at these levels, adverse effects seem to be extremely rare and mild. In most studies, no participants reported side effects. We’ve only seen one study in which a small number (6.7%) of participants had to leave the study due to adverse effects (source).
As we explained above, B12 is routinely taken as an oral supplement in amounts exceeding 400 times your recommended daily intake.
Clinical trials have established that it is safe and relatively side-effect-free in doses of up to 2,000 mcg per day. We have no idea why anybody would consume that much B12 unless they were participating in a clinical trial of course!
So on the whole, it does not look like it is dangerous to consume large quantities of B12.
That goes for regular, daily B12 supplementation too.
However, there are some caveats that we need to talk about.
We recently came across one study in which researchers found that a folic acid, B6 and B12 stack raised the occurrence of vascular events in people with diabetic nephropathy (source). In simpler terms, large doses of B12 were associated with an increased incidence of cardiovascular events in people with diabetes-induced kidney damage.
It is also true that a small minority of people are prone to experiencing side effects when they consume relatively large quantities of B12.
The side effects of consuming too much B12 can be very similar to the symptoms of B12 deficiency – muscle tingling, muscle aches, sudden energy crashes, skin redness, and more.
However, we stress that the occurrence of side effects from B12 – within the normal dosing range – is extremely rare.
There are no known long-term health risks associated with regular B12 consumption.
SHOULD YOU BE USING A B12 SUPPLEMENT?
Whether or not you should be using a B12 supplement obviously depends on your own needs, goals, and physical condition.
If you are a highly active person, then you could probably benefit from adding some supplemental B12 into your diet.
If you are a vegan or vegetarian, it might be a good idea to eat more B12-fortified foods. If you can’t get enough of those, then a good quality B12 supplement is an easy, cost-effective, safe solution.
Of course, if you want to optimize performance as much as possible, then it’s a good idea to take a high-quality multivitamin on a daily basis. B12 should always be present in a quality multivitamin.
But if you aren’t looking to maximize performance or to rectify a potential B12 deficiency, then there is no need to use a B12 supplement. Just eat a healthy, balanced, well-planned diet and you’ll be fine.