Maybe you see vitamin B12 on your multivitamin label and give yourself kudos for getting your fill in one handy pill; maybe you’re a seasoned vegan who sprinkles B12-fortified nutritional yeast on practically everything; or maybe you haven’t even given B12 a second thought.

If you fall into that last camp (many of us do), know this: There’s a reason most multis pack high amounts of B12. This buzzy vitamin is crucial for your overall health and well-being—and certain groups of people might need more vitamin B12 than others.

Vitamin B12 Background

Vitamin B12 is essential for the formation of red blood cells, which deliver oxygen to tissues and organs, explains nutritionist Staci Gulbin, M.S., ME.d., R.D.N. “B12 is also important for brain and central nervous system function and DNA synthesis.”

Falling short on B12 can lead to a host of problems, ranging from fatigue and anemia to cognitive issues and weakness. What’s more, “vitamin B12 deficiency is thought to be under-diagnosed in America and around the world,” says Gulbin.

Common signs of B12 deficiency include fatigue, paleness, weakness, weight loss, and irritability, according to Amanda A. Kostro Miller, R.D., L.D.N., nutrition advisor for Smart Healthy Living. Iron deficiency can also indicate lack of B12.

Read More: 6 Surprising Causes Of Vitamin B12 Deficiency

“If you are concerned that you have a B12 deficiency, don’t self-diagnose,” she says. “B12 deficiencies mimic many other deficiencies.” Luckily your doctor can confirm deficiency with a simple blood test.

Animal products like beef, chicken, fish, and dairy are our only food sources of B12—so products like almond milk and cereal fortified with it.

People Who Might Need More B12

Given the limited sources of B12 and health concerns that affect absorption of the vitamin, certain groups of people may need to pay extra attention to their B12 intake.

1. Vegetarians and Vegans

If you don’t eat meat, it’s important that you prioritize eating B12-containing dairy products. “B12 foods for vegetarians include dairy, particularly milk and yogurt,” says dietitian Jennifer Hanes, MS, RDN, LD. “Cheese and eggs contain smaller amounts.”

Vegans, however, have to depend on fortified foods such as nutritional yeast or plant-based milks, likely combined with a supplement, Hanes says. If you don’t eat any animal products, consider having your B12 levels tested and working with a nutritionist to create a game plan for keeping your levels healthy.

2. Athletes

Athletes who regularly consume animal foods likely meet their B12 needs. However, athletes who restrict calories (like bodybuilders or wrestlers) or certain foods put themselves at especially high risk for a number of nutrient deficiencies, B12 included, says Kostro Miller.

Athletes should be cognizant of fatigue, weakness, and other signs of B12 deficiency.

3. People With Gastrointestinal Issues

“Conditions that compromise gut integrity can increase your risk of B12 deficiency due to poor digestion and absorption,” says Kostro Miller.

In the case of Crohn’s disease—a chronic inflammatory bowel disease of the digestive tract—many B12-rich foods can also trigger abdominal pain or diarrhea.

Read More: 5 Steps To A Happier, Healthier Gut

People who have undergone any type of gastrointestinal surgery may also need to be more conscientious about getting adequate B12 since these procedures can lead to declines in nutrient absorption, explains dietitian Erika Fox, M.B.A., R.D.N., of 310 Nutrition.

4. The Elderly

“As we age, the intrinsic factor [a substance made by the stomach to help the body absorb vitamin B12] in our stomachs becomes depleted,” explains dietitian Jeani Hunt-Gibbon M.S., R.D., C.D.

As a result, older adults are more likely to suffer from B12 deficiencies. Some studies estimate that up to 40 percent of seniors are deficient in the vitamin. (Others suggest the number falls closer to 20 percent.)

5. People Who Take Certain Medications

Finally, taking certain medications may also make you vulnerable to B12 deficiency, according to Harvard Medical School. Proton-pump inhibitors (PPIs), which are often used to help address acid reflux and heartburn, for example, increase risk of deficiency.

How To Up Your B12 Intake

The average adult who eats animal products daily will likely meet their daily vitamin B12 needs (2.4 micrograms) without too much effort. (Three ounces of salmon, for example, provides more than double the daily value of B12, according to Hunt-Gibbon.)

If animal products are off the table (or even mostly off the table), make sure to consume products that have been fortified with B12. A serving of Cheerios, for instance, provides 25 percent of the daily value.

Finally, if you can’t meet your B12 needs through food alone, consider adding a supplement to your routine. If you already take a multivitamin (or have other nutrient concerns), that should do the trick. However, you can also look into a stand-alone vitamin B12 supplement.

You’ll see B12 supplements in either methylcobalamin and cyanocobalamin form. Though both have been shown to successfully remedy B12 deficiency, methylcobalamin is more bioavailable and may be more beneficial for people with various absorption issues, suggests Kostro Miller. (We recommend Vthrive The Vitamin Shoppe brand Bioactive B-Complex, which also contains other B vitamins, such as thiamine, riboflavin, and biotin.)

Rest assured that since there’s no upper limit for B12, you can consume more than the RDA (most supplements contain high amounts of the stuff) without issue.

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