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Here’s how to tell if you may be deficient in B12 and what to know before you opt for a supplement.

This article was medically reviewed by Marjorie Cohn, M.S., R.D.N., a certified integrative and functional medical nutrition therapist and member of the Prevention Medical Review Board.

If you’ve been feeling unusually sluggish and weak or if you can’t seem to stay awake during the day, you may be wondering if you’re getting enough of your essential nutrients. A big one to watch: vitamin B12, especially if you follow a plant-based diet. While you can get vitamin B12 from foods, you can also get your recommended dosage by having one of the best B12 supplements (but more on that later).

Also known as cobalamin, think of vitamin B12 as fuel for your engine—it plays essential roles in energy production within your body, says Stephanie Gray, D.N.P., M.S., A.R.N.P., a doctorally prepared functional medicine nurse practitioner and owner of Integrative Health and Hormone Clinic in Hiawatha, IA. It also tamps down chronic inflammation within the cardiovascular system (that can, in turn, lower heart disease risk), helps maintain the nervous system (including the myelin sheath, “insulation” that surrounds nerves), and produces neurotransmitters (a.k.a. your body’s chemicals messengers).

“Vitamin B12 is necessary for normal processing of carbs, proteins, and fats in the body and for the normal formation of red blood cells,” adds Elizabeth Somer, M.S., R.D.N., a dietitian based in Salem, OR and a medical advisory board member for Persona Nutrition. “It’s essential for the replication and maintenance of all body cells.”

Most adults should aim for at least 2.4 micrograms per day, according to the National Institutes of Health (NIH). However, it’s recommended that people who are pregnant or breastfeeding have 2.6 and 2.8 micrograms of B12 a day, respectively, the NIH says.

It is possible to hit your daily recommended vitamin B12 amount through your diet. Vitamin B12 is naturally present in animal foods like fish, meat, poultry, eggs, and dairy products, the NIH says, but you can also find it in some fortified breakfast cereals and fortified nutritional yeasts.

Here’s a breakdown of some of the top sources:

“It’s not found in plant foods, unless those foods are either fortified, such as fortified soymilk, or fermented, such as tempeh,” Somer says.

A big group that could potentially benefit from a vitamin B12 supplement is vegetarians and vegans, says Keri Gans, M.S., R.D., author of The Small Change Diet. “B12 is more available in animal products,” she points out.

People with digestive issues like Celiac disease and Crohn’s disease or “any kind of malabsorptive condition” may need to supplement as well, says Jessica Cording, M.S., R.D., author of The Little Book of Game-Changers.

Older adults, people who have had certain gastrointestinal surgeries, and those with pernicious anemia, an autoimmune disease where the body can’t make enough healthy red blood cells, may also benefit from a B12 supplement, the NIH says.

Since the symptoms of a vitamin B12 deficiency are fairly common—especially mid-pandemic—it can be challenging to determine if your levels are too low. Symptoms are broad and include fatigue, weakness, loss of appetite, weight loss, and pernicious or megaloblastic anemia. “Nerve problems, such as numbness and tingling in the hands and feet, are also a risk,” Somer says. “Over time, a deficiency of B12 can cause problems with balance, confusion, depression, poor memory and [possibly] dementia, and it can even cause permanent damage to the nervous system. That means treating a deficiency as soon as possible is crucial.”

A deficiency can result from several causes:

“While poor intake is rare, poor absorption is not uncommon, especially as people age. As a result, about 15% of Americans are low in vitamin B12,” Somer says. A physician can order blood tests to assess your vitamin B12 status, but if you suspect a nutrient deficiency, a comprehensive nutritional analysis may also be beneficial, Gray says.

Since the symptoms of a vitamin B12 deficiency are fairly common—especially mid-pandemic—it can be challenging to determine if your levels are too low. However, Johns Hopkins Medicine says that these are more common symptoms of vitamin B12 deficiency anemia, which is a condition where your body does not have enough healthy red blood cells, due to a lack of B12:

While you could guess that you may be low in vitamin B12, the best way to really know your status is to talk to your doctor. “The best way to find out if you are deficient is to have your doctor conduct a blood test,” Gans says.

Cording agrees. “If you’re having symptoms of low B12 and you’re not eating a lot of B12 foods, talk to your doctor about testing your levels,” she says.

Because vitamin B12 is water soluble (meaning it dissolves in water and is excreted in your urine), “vitamin B12 supplements are very safe even at doses several times the recommended dietary allowances,” Somer says. “Like all vitamins, B12 works best with its team of other nutrients. So taking it in a multivitamin is best, unless you have been diagnosed with a deficiency. In that case, a physician might prescribe large doses to correct the deficiency, followed by a lower maintenance dose.”

If you do require a vitamin B12 supplement, follow this advice from our experts:

✔️ Seek out methylcobalamin. Most vitamin B12 supplements contain cyanocobalamin, which contain trace amounts of cyanide, Somer says. It’s also far less efficient than supplements made with methylcobalamin. “In order for cyanocobalamin-based B12 supplements to be utilized in the body, the liver must first remove the cyanide molecule and attach a methyl group to form methylcobalamin, the biologically active, tissue-ready form. Research has shown that methylcobalamin is more efficiently used and retained in the body than the cyanocobalamin form,” Gray says.

✔️ Read the label. The form of B12 should be clearly listed. Ditch the “cyano” (yes, even though it’s often the most affordable) and switch to safer “methyl” or new “hydrozyl” forms, Gray suggests. In addition, look for “a capsule or liquid form taken under the tongue since they work quicker than tablets.”

✔️ Ask about other B deficiencies. Many times when individuals need more vitamin B12, they are also shy in other B vitamins as well, like B9 and B6. Ask your doctor if a B complex is the right fit.

✔️ Make sure it’s easy to use. This, Cording says, is huge. “If you know you have trouble swallowing pills, it can be helpful to look for a sublingual product where it dissolves under your tongue or to use a spray or liquid,” she says.

✔️ Pay attention to dosing. Again, the daily recommended dietary allowance of vitamin B12 for most adults is 2.4 micrograms, stretching up to 2.6 and 2.8 micrograms if you’re pregnant or nursing. However, your doctor may recommend different dosing depending on your individual needs. “Don’t exceed the recommended dose unless you have discussed it with your physician,” Gans says.

Now that you know what to keep in mind, the following B12 supplements all feature highly-absorbable forms of the vital vitamin.

With Gray’s stamp of approval, these capsules come highly recommended by people who are popping 1 to 3 of them daily due to the lack of sketchy filler ingredients and ability to noticeably boost energy levels. Bonus: They’re also gluten-free.

Made with methylcobalamin and oodles of organic fruit and botanicals, one spray a day tastes like raspberries while delivering 500 micrograms of vitamin B12.

Easy to swallow with little to no aftertaste, these softgels are easy to add to your daily routine—even if you’re not typically the supplementing type. Pair with a glass of water and a meal and you may experience less fatigue in a month or so, reviewers say.

For a little extra bone boost with your B12, consider this methylcobalamin supplement that comes paired with a bit of calcium. Pop one daily with food and you may feel more energetic, happier, and sleep sounder as a result, as reviewers rave.

If you notice your vitamin B12 deficiency is impacting your ability to sleep, try these Gray-approved capsules, which are said to support the natural circadian rhythm and promote more normal sleep cycles when you take 1 to 3 per day.

With a two-month supply in each bottle, these vegan drops are a great option for those who struggle with popping pills. Add a citrus-flavored drop under your tongue, drink a glass of water, and you’re well on your way to more energy and a sharper memory, according to those who take it daily.

Another under-the-tongue liquid option, add five drops to your daily agenda for an easily-absorbable vegan supplement that might aid in digestion and result in healthier hair, skin, and nails while supporting cognition and the nervous system.

Loaded with B2, B6, B12 and folate, this multipurpose supplement will help cover your bases if you are diagnosed with multiple B deficiencies. Some oral contraceptives and anti-inflammatory medicines can deplete blood levels of all of the above, making this an especially wise choice for some women.