vitamin b12 is a water-soluble vitamin that the body needs in small amounts to function and stay healthy. It is essential to make red blood cells, RNA and DNA, and to help the nervous system work properly. It also helps with cellular growth, energy production, and the creation of tissues.

It can be found naturally in meat, eggs, poultry, fish, dairy products and fortified foods. It’s also produced by certain bacteria and available as a supplement or prescription medication.

The vitamin’s main role is to make red blood cells, which carry oxygen throughout the body. But it can also play a vital role in metabolizing protein, carbohydrates and fats.

In addition, it helps with the formation of nerves in the brain and spinal cord. If a person doesn’t get enough vitamin B12, they can experience numbness, tingling or loss of coordination in their hands and feet. It can affect the function of the intestines, which can result in constipation or diarrhea.

Deficiency symptoms can be mild or severe, but they should always be treated by a medical professional. They may include a lack of appetite, fatigue, depression, headaches and mood changes. If you think you may be lacking vitamin B12, talk to your doctor.

Some diseases can increase your risk for a vitamin B12 deficiency, such as pernicious anemia and celiac disease. These autoimmune diseases attack the body’s digestive tract, and can lead to an inability to absorb vitamin B12 from your diet. This can be especially true if you’ve had intestinal surgeries that affected the stomach or ileum where vitamin B12 is absorbed, says Graber.

If you have a deficiency, your doctor can test your blood for B12 levels and check for signs of other conditions. They can also order a methylmalonic acid (MMA) or total homocysteine test, which measures the amount of this amino acid in your blood.

Homocysteine is a dangerous amino acid that can build up in the blood and damage the walls of arteries, which can cause heart disease. Taking vitamin B12 supplements along with folate, another B-vitamin, can lower this amino acid, according to the Cleveland Clinic.

Low levels of vitamin B12 can cause a variety of symptoms, including anemia, skin rashes, memory problems and even paranoia or hallucinations. Some people with these problems can’t tell that they are deficient, so it’s best to have a checkup to make sure you’re not dealing with an underlying health issue.

Vitamin B12 is also essential for women who are pregnant or planning to become pregnant, because it helps to prevent low birth weight in the fetus and infant. It can also help reduce complications of pregnancy and reduce labor and delivery time.

Other common symptoms of a vitamin B12 deficiency include fatigue, headaches and loss of balance. It can also lead to numbness or tingling in the hands or feet, and a change in mood.

The risk of a vitamin B12 deficiency increases with age, if you’re pregnant or have a child in the womb, and if you’re taking medications that affect your gastrointestinal (GI) health. Some GI drugs, such as proton pump inhibitors and H2 receptor antagonists, can reduce the absorption of vitamin B12 in the stomach and intestines.