The first thing that you need to know about vitamin B12 is that it is an essential, water-soluble vitamin, so even if you are consuming “too much,” your body takes what it needs and passes what it doesn’t through your urine. That shouldn’t be an excuse, though, for overdoing vitamin B12. Most Americans are getting at least the minimal amount recommended by the government; however, there are still many of us who aren’t even reaching that goal.
Before we start talking numbers, let’s first review the reasons why you need vitamin B12. One of eight B vitamins, B12 is also known as cobalamin. Its scientific status as “essential” means that your body doesn’t produce the vitamin on its own. But not to worry—there are several foods that naturally contain B12, including fish, beef and beef liver, chicken, eggs and even some dairy products such as milk. You can also get B12 from specific cereals, those that indicate on the box label that they are fortified with the vitamin.
In addition to these foods, many people choose to add nutritional supplements with B12 to their diet. In this case, make sure you keep watch on how much vitamin B12 you’re getting and from where. For example, your multivitamin is likely to have B12 in it, usually above the recommended daily amount. So, if you choose to add a B complex vitamin (generally a combination of several B vitamins) or a single nutrient vitamin (one with only B12), be aware that your B12 intake will add up quickly.
In addition to your diet, there are also B12 injections, nose sprays, nasal gels, sublingual medications and prescriptions. These options are probably more appropriate for those who know they are falling short in vitamin B12 and should be discussed with a doctor.
How Much B12 Can I Take a Day?
In layman’s terms, vitamin B12 is considered essential because it is vital to your body’s functioning properly. For example, B12 is one of the vitamins that manufactures the DNA that goes into your body’s tens of trillions of cells; without enough of it, these cells aren’t able to do their job. As importantly, vitamin B12 helps produce the red blood cells that carry oxygen throughout your body.
On top of those basic—but not so basic—jobs, some research (but not all) has indicated that B12 (at higher doses than the daily recommendations) may help with mood disorders and cognition, from depression to memory loss, and possibly dementia. B12 also helps prevent a red blood cell condition—anemia—that creates exhaustion and extreme fatigue. And let’s not forget that B12 helps convert your food into energy.
The recommended amount of vitamin B12 is 2.4 mcg daily for those age 14 and over—less for those under 14; 2.6 mcg for pregnant women; 2.8 mcg for those who are breastfeeding. While a vitamin B12 deficiency is rare in the U.S., vegetarians and vegans may be at risk of deficiency because of their plant-based diets.
In addition, as you age, absorbing vitamin B12 becomes more difficult for some, putting seniors at greater risk for deficiency. Others at risk include heavy drinkers, those with digestive track conditions, or certain immune system disorders, according to this article which lists some other categories of people who should be aware that they may not be getting enough vitamin B12.
What you really want to strive for is what some experts consider an “optimal” amount, getting not only the daily recommended intake of B12 that helps ensure basic bodily functions, but consuming above that recommendation to potentially access some of the benefits that research has demonstrated at higher doses, even above the recommended dietary allowance.
What Happens if Your B12 is Too High?
As mentioned earlier, it’s not hard to go above the recommended dietary allowance. And it’s not necessarily bad to do that. But what happens if you’re continually mega-dosing? There are some consequences of getting too much vitamin B12, even though the vitamin is believed to be safe, even at high daily doses.
Let’s explore that. Tolerable Upper Intake Levels (or ULs) refer to the highest level of nutrient intake that does not pose any adverse health effects for the majority of people. In the case of vitamin B12, there has been no UL identified—and that’s because the vitamin is believed to have a low toxicity level.
But even without a UL for vitamin B12, that doesn’t mean you should megadose the nutrient. You know the saying: just because you can doesn’t mean you should. There are some potential side effects of “too much” B12 to look out for.
For example, some research has shown that getting too much vitamin B12 is associated with acne or rosacea, although this article advises those studies were focused on high-dose B12 injections rather than vitamin B12 supplements.
Other studies point to issues from high vitamin B12 levels, including greater risk of cardiovascular issues and diabetic nephropathy. And this post warns that high doses of vitamin B12 can lead to headaches, fatigue, nausea, and tingling in the hands and feet.
On the other hand, research has demonstrated that oral nutritional supplements containing up to 2,000 mcg daily of vitamin B12 supplements are safe and can be effective in reversing a B12 deficiency.
So, you may be wondering: “How much B12 can I take in a day?” Here’s our suggestion.
Testing is the Answer
There really is only one way to find out whether you are B12 deficient, sufficient, optimal or getting too much. And that is to test regularly to better understand your vitamin B12 status. Once you know your numbers, you can make adjustments to increase or decrease your body’s B12.
There is more than one way to test. Your doctor can order a blood test for you. In fact, your doctor may order this test along with other testing during your annual physical, especially if he or she has reason to suspect that you may be deficient. And if you have questions, don’t be shy about discussing your vitamin B12 intake with your doctor because it’s not just a B12 deficiency that can be identified by testing.
A serum B12 level between 300 pg/mL and 900 pg/mL is what is considered normal, according to this article, while results above 900 pg/mL are considered high. If your B12 status is extremely high, it might be a signal that you have a serious issue such as leukemia, diabetes or liver disease.
There are also at-home tests available to determine your B12 status, including one from OmegaQuant that tests your urine. Our test measures methylmalonic acid (MMA) in the urine rather than in the blood. The results are reported in units of mmol MMA/mol creatinine (cr). If your MMA results are above 3.8 mmol/mol cr, it means that your B12 status is very low and further testing is strongly suggested.
Your goal is for your MMA results to be below 2.0 mmol/mol cr because those numbers indicate your vitamin B12 status is optimal. At OmegaQuant we recommend you take this test every four to six months to ensure you remain in optimal status.
Testing not only identifies whether you are too low, too high, or just right but also provides the opportunity to correct problems before they aren’t easily correctable. And keep in mind that while vitamin B12, even at high doses, is likely safe, if your numbers show you are in optimal range, you probably don’t need to be mega-dosing. Just because a little is good doesn’t mean a lot is better.