What to Know If You're Considering B12 Shots

B12 shots are usually made of cyanocobalamin, a synthetic form of the vitamin. Some B12 shots may also contain hydroxocobalamin, another synthetic form. Both types are inactive, meaning the body must convert the injection into another form to make use of it. There are a few shots on the market that contain methylcobalamin or adenosylcobalamin, the active and natural forms of B12, but these really only work when taken or created together. In addition, there isn't much evidence of their effectiveness in a supplement or injectable form.

B12 shots are concentrated forms of the vitamin that the body uses to create red blood cells and DNA. This important nutrient also helps the body maintain the central nervous system. Many people do not consume or absorb enough vitamin B12, people eating plant-based diets, for example. Injections can quickly resolve this problem and prevent issues like anemia.

A B12 deficiency often presents with symptoms such as neurological problems, decreased motor function, and problems with balance. One of the most common signs of low B12 levels is pernicious anemia. This condition occurs in people who have trouble absorbing B12, which causes a low red blood cell count. In adults, some of the symptoms include irritability, motor problems that lead to difficulty walking and eating, depression, brain fog, mouth ulcers, weight loss, and digestive problems. In infants and young children, pernicious anemia and low B12 can cause developmental problems.

In the U.S., poor absorption causes more B12 deficiency than diet does. Some B12 utilization disorders are hereditary, so people with a family history of low B12 levels or poor absorption should be tested for deficiencies. Many adults with pernicious anemia or a related disorder might consider B12 shots, at least initially, to quickly increase their levels of the nutrient and prevent the progression of symptoms. People who follow a vegan diet may need to get B12 shots since the vitamin is largely nonexistent in plants and plant-based products unless deliberately added. However, vegans who don't have difficulty absorbing the vitamin can take an oral supplement instead. Older adults often experience B12 deficiency as they age, so doctors may recommend injections.

Most people with a B12 deficiency will benefit from a shot. Some people should not have them, though. Anyone allergic to cyanocobalamin, hydroxocobalamin, or cobalt should avoid B12 injections, and people with Leber's hereditary optic neuropathy or kidney disease should check with a doctor first. Parents considering them for their child, pregnant women, and people who consume alcohol, should consult a doctor before starting B12 injections. People who take medication should also talk to their physician before having a B12 shot, to ensure these drugs don't interact poorly or negate the effects of the shot.

A physician prescribes B12 shots. Once you meet with your physician and have a prescription, you can schedule an appointment at a clinic or at a doctor's office. You may also be able to find B12 kits and administer your own injections, although this isn't recommended for most people.

People with serious, chronic, or hereditary B12 deficiencies may receive shots over the course of their lifetime. People with anemia as a result of a B12 deficiency usually start with daily shots for about a week, then taper to every few days, then move to monthly shots. Consult with your physician to find the best schedule for you.

Most people who receive B12 injections don't experience any adverse effects. Some people, however, develop diarrhea or feel swollen after the shot. Problems like these are often short-lived and resolve without professional help. Call a doctor promptly about muscle weakness or cramps, extreme thirst, frequent urination, confusion, a fast heartbeat, or shortness of breath. Hives, rash, itching, or trouble breathing or swallowing signal an allergic reaction and need immediate care.

Vitamin B12 occurs naturally in animal-based products and this is often the best, most efficient source. B12-rich foods include eggs, meat, fish, poultry, milk, and cheese. Some foods are fortified with B12 even if the food doesn't normally contain it. There are also multivitamins that contain numerous vitamins, including B12.

Supplements are often just as effective as B12 shots. Some research has found supplements in the form of prescription pills to be more affordable, and people with an aversion to needles may prefer to receive their doses as pills. On the other hand, pills must be taken more frequently than a monthly shot, so some people may prefer the latter to remembering to take a supplement. Plus, people who have digestive issues that reduce the absorption of vitamin B12 may get more benefits from an injection.