In a perfect world, you’d get all the vitamins, minerals and nutrients you need just by eating the right foods. In fact, the Dietary Guidelines for Americans recommends that you meet your nutritional needs mostly through a healthy diet. That’s because food delivers things that are essential for good health that supplements simply can’t.

For example, foods such as beans, nuts, oats, fruits and vegetables have dietary fiber, which helps prevent heart disease, cancer and other diseases. Fruits and veggies also give you antioxidants. These are natural compounds that help keep your cells healthy and repair damage.

But following a perfect diet day after day is difficult even for the healthiest eaters. And sometimes, there are factors you can’t control that make it tough to maintain healthy levels of certain nutrients. That’s true with vitamin B, which is actually 8 different vitamins that include:

  • B-1 (thiamine)
  • B-2 (riboflavin)
  • B-3 (niacin)
  • B-5 (pantothenic acid)
  • B-6 (pyridoxine)
  • B-7 (biotin)
  • B-9 (folate)
  • B-12 (cobalamin)

Of those, there are 2 you should keep an extra-close eye on: B-12 and folate. They both play a key role in making red blood cells, DNA and more. Older adults have a harder time absorbing vitamin B-12. In fact, as many as 38% of older adults have B-12 levels that are too low, according to a study in Current Opinion in Clinical Nutrition and Metabolic Care.

Plus, certain common medications, such as those for heartburn and acid reflux, also reduce B-12 absorption. And pregnant women and people with digestive issues such as celiac disease are at risk for folate deficiency.

We talked to Rosanna Sutherby, PharmD, a community pharmacist and medical writer based in High Point, North Carolina, to get her thoughts on who can benefit from different kinds of vitamin B supplements. She also weighs in on when a prescription might be better than an over-the-counter supplement. (Download the Optum Perks app to access coupons for thousands of medications, prescription supplements included.)

Question: Why are B vitamins important for health?

Sutherby: The B vitamins each have different functions in your body and for your health. They help with nervous system function by coating the nerve cells so that they can function properly. They help you use energy from food. Some of them help you absorb other vitamins. They help you with digestion and muscle tone. They make red blood cells that transport oxygen throughout your bloodstream to your organs.

Q: When might a vitamin B complex or B-12 supplement be recommended?

Sutherby: There are several times you might need to supplement with B vitamins:

Vitamin B deficiency: During a regular checkup, you may get a blood test that helps evaluate your health. Your health care provider might notice that you are deficient in certain vitamins. Sometimes, people may be deficient in several B vitamins, and a health care provider may recommend taking a vitamin B complex, which has all the B vitamins in it. (Get a coupon for vitamin B complex now.)

But you don’t necessarily need them all. Although B vitamins are water-soluble and your body gets rid of any extra, some can cause harm if you take too much. For example, too much vitamin B-3 (niacin) can cause flushing of the skin. Taking high doses for too long can damage your liver. Getting too much vitamin B-6 can cause a type of nerve damage called peripheral neuropathy. High doses of folic acid can hide the symptoms of vitamin B-12 deficiency. Untreated vitamin B-12 deficiency can lead to nervous system damage.

It is usually best to only take a vitamin B complex if you know you are low in several B vitamins, including vitamins B-6 and B-12, niacin and folic acid. Otherwise, it is safer to supplement only the vitamins that are deficient.

One of the symptoms of being deficient in some kinds of B vitamins, specifically B-12 or folate, is feeling tired and drained. Your doctor can check your vitamin levels. If your hemoglobin (a protein in red blood cells) is low, you may need B-12 or folic acid.

Low hemoglobin levels can also be a sign of folate-deficiency anemia, also called megaloblastic anemia. Other signs of this type of anemia include larger than normal red blood cells and low folate levels.

Healthcare providers may use folic acid to treat several conditions, including megaloblastic anemia and depression, as well to decrease the risk of heart disease or certain birth defects.

Pernicious anemia: There are conditions in which your body doesn’t absorb the B vitamins very well. One of these conditions is called pernicious anemia. People with pernicious anemia cannot absorb vitamin B-12 when taken orally. They would need a B-12 injection rather than an oral supplement (to bypass the digestive process).

Older adults: The pH in your stomach (a measure of how acidic your stomach fluids are), may rise as you get older. That makes it harder to absorb vitamin B-12. Older adults may need either higher doses of an oral supplement or vitamin B-12 shots.

Past bariatric surgery: People who have had bariatric (stomach) surgery to help them lose weight may need B-12. With that surgery, you may have lost part of your stomach and some ability to absorb vitamin B-12. A B-12 shot would be beneficial once you’ve been tested to see that you truly are low.

Gastrointestinal disease: People with conditions such as Crohn’s disease and celiac disease might benefit from B-12 shots. That’s because gastrointestinal diseases interfere with the absorption of vitamin B-12.

Vegetarians and vegans: You can get most B vitamins through plant-based foods, except for B-12. B-12 can only be obtained from animal sources, such as meat, eggs and dairy — or from supplements. Someone who follows a strict vegan or vegetarian diet might benefit from vitamin B supplements.

Pregnancy: The Food and Nutrition Board at the National Academies of Sciences, Engineering, and Medicine recommends that all women of childbearing age take 400 micrograms of folic acid daily. During pregnancy, you need 600 to 1,000 micrograms of folic acid daily. Folate is essential for the healthy development of a baby’s brain and spinal column. Getting enough of this vitamin before and during your pregnancy helps prevent certain types of birth abnormalities.

Q: What types of vitamin B supplements are available by prescription?

Sutherby: The vitamin B-12 shot and higher doses of folic acid are available by prescription. The B-12 shot is called cyanocobalamin. Folic acid is the synthetic form of folate, which you can also get from fortified foods.

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Q: What are some of the benefits of vitamin B-12 shots?

Sutherby: The biggest benefit is that you would get your vitamin B-12 without having to worry about absorbing it in your stomach. With a shot, it goes right into the bloodstream, so your body can use it immediately.

Also, the shots are usually once a week, sometimes twice a week, depending on how low your levels are. As far as dosing, you don’t have to worry about taking a pill every day.

B-12 can be given intramuscularly (into the muscle) or subcutaneously (under the skin). You just pinch the skin, like giving an insulin shot. Sometimes people go to the doctor to get their shots. But for the most part, people do their own B-12 shots at home or at the pharmacy.

Q: What are the potential side effects of B-12 shots?

Sutherby: As with any other shot, you might experience redness at the injection site, maybe a little itching. Severe side effects include your skin turning blue, chest tightness or difficulty breathing. Less severe side effects include headaches or diarrhea.

The biggest thing that we worry about with any shot is an allergic reaction to the injection. This causes a rash, itching, hives, and swelling of the lips, face or tongue. That would be considered an anaphylactic reaction, and you would need emergency help.

Q: Can these shots interact with other medications?

Sutherby: If you’re taking colchicine, a medication used to treat gout, you should talk to your doctor before getting a B-12 shot.

Q: Do you have any advice for people considering vitamin B shots?

Sutherby: I wouldn’t recommend just taking a supplement on your own. Always check with your health care provider to see what your vitamin B levels are. Don’t just assume that they’re low.

I also wouldn’t automatically go to a shot. If you have problems absorbing the vitamin for whatever reason, then go to the shot. But if you can get by with an oral supplement, I would start there.

Want to keep reading up on B? Learn more about the surprising benefits of folic acid now.

Additional sources
Nutrition basics: USDA Dietary Guidelines for Americans 2020-2025
Deficiency among older adults: Current Opinion in Clinical Nutrition & Metabolic Care (2010). “Vitamin B12 and older adults.”
B vitamin deficiencies: Harvard Health and Johns Hopkins Medicine