What Are the Symptoms of B12 Deficiency?

  • Medical Reviewer: Dany Paul Baby, MD
Medically Reviewed on 7/29/2022

What is a vitamin B12 deficiency?

Vitamin B12, also called cobalamin, is a nutrient you get from eating animal products. The symptoms of B12 deficiency tiredness, muscle weakness, mouth ulcers, and other symptoms.
Vitamin B12, also called cobalamin, is a nutrient you get from eating animal products. The symptoms of B12 deficiency tiredness, muscle weakness, mouth ulcers, and other symptoms.

Vitamin B12, also called cobalamin, is a nutrient you get from eating animal products. A similar nutrient is B9 or folate. It’s a naturally-occurring substance that helps your body create new DNA and red blood cells. If you’re not getting enough of this vitamin, you may experience vitamin B12 deficiency anemia. Here’s what you need to know.

Vitamin B12 is found in animal products like meat, fish, and dairy. It sticks to the proteins in these foods, and then hydrochloric acids and enzymes in your stomach release it into its free form. B12 creates red blood cells that carry oxygen around your body. If your body doesn’t have enough red blood cells, your organs and tissues don’t get the oxygen needed to function properly. When this happens, it’s called anemia.

There are different kinds of anemia. Anemia caused by a lack of vitamin B12 or folic acid is called megaloblastic anemia. It causes your body to produce red blood cells that are too big and don’t function correctly. Anemia can also happen because your body isn’t making enough red blood cells or there is a low amount of hemoglobin inside the red blood cells.

The Recommended Daily Allowance (RDA) for men and women over 14 years is 2.4 micrograms of vitamin B12 per day. Pregnant women should increase their intake to 2.6 micrograms, and women who are lactating should go up to 2.8 micrograms. There currently isn’t a daily maximum since it’s not toxic, and vitamin B12 has no harmful side effects for most people.

What are the symptoms of a B12 deficiency?

Developing anemia due to a B12 deficiency can take place over months to years. Because of this, you may not even have any noticeable symptoms, or symptoms that are very mild.

Your body relies on vitamin B12 and folate to carry out several bodily functions, including maintaining the health and function of your nervous system. Without enough of these vitamins, you may start to notice some of these physical symptoms:

B12 deficiency anemia may also cause some mental symptoms. You may experience:

Since these symptoms can occur without anemia, you need to talk to your doctor to get to the root cause.

What causes B12 deficiency?

A vitamin B12 deficiency is caused by not eating enough foods that contain this vitamin. Good sources of vitamin B12 include:

  • Eggs
  • Meat
  • Poultry
  • Fish
  • Shellfish
  • Dairy
  • Fortified cereals

You may have a lack of intrinsic factor. This protein is created in your stomach and helps your body absorb vitamin B12 from the foods you eat. If your body cannot make intrinsic factor, it could be because of chronic gastritis or certain autoimmune conditions. Some people can’t absorb this vitamin due to surgery on the small intestine or changes in the small bowel.

Risk factors. Some people may be at more risk of developing vitamin B12 deficiency anemia. People who follow vegan, vegetarian, or fad diets are more likely to develop this vitamin deficiency since they eat little or no animal products. People who have a long history of not eating well or not eating a varied diet are also at risk.

Other risk factors include:

  • Certain medications
  • HIV
  • Crohn’s disease
  • Being an older adult
  • A family history of vitamin B12 deficiency anemia
  • Having your stomach or intestine removed due to surgery


Next to red peppers, you can get the most vitamin C from ________________. See Answer

How is vitamin B12 deficiency anemia diagnosed and treated?

Diagnosing vitamin B12 deficiency can be tricky since some symptoms are similar to those of other conditions and nutrient deficiencies, and some people have no symptoms at all. To determine if you have this vitamin deficiency, your doctor will perform some blood tests to check your vitamin B12 levels.

First, your doctor will give you a physical exam and then ask about your health history and symptoms. They will then perform a complete blood count (CBC) along with a specific test that looks at the levels of vitamin B12 in your blood. People who are considered vitamin B12 deficient if their count is less than 150 per milliliter.

Treatment. In most cases, a vitamin B12 deficiency can be easily treated. Your treatment will depend on several factors, such as:

  • Your age
  • How serious your symptoms are
  • Your reactions to certain medications and treatments
  • Your health and medical history
  • Your preferences

Vitamin B12 and folate deficiencies are hard to tell apart and often happen at the same time. Your doctor will increase your intake of these vitamins in several ways. When it comes to vitamin B12, most doctors suggest cyanocobalamin, a manmade form of B12 that comes in pill form. Other possible treatments include:

  • Vitamin B12 injections
  • Nasal spray or gel with vitamin B12
  • Oral medication

Your doctor may also recommend folic acid pills if you have this deficiency, along with a vitamin B12 deficiency.

Preventing vitamin B12 deficiency 

The good news is that this kind of vitamin deficiency is avoidable for most people. People who are not vegan or vegetarian should eat a balanced diet that includes a healthy mix of animal products. If you are following a vegan or vegetarian diet, you should eat grain and cereal products that are fortified with vitamin B12 or take a daily dietary supplement.

To make sure that you’re getting enough folic acid, try adding some of these foods to your diet:

  • Oranges and orange juice
  • Leafy greens like lettuce and spinach
  • Legumes and soy products
  • Rice, barley, and wheat germ
  • Green veggies
  • Sprouts
  • Liver

Poor vitamin B12 absorption is linked to digestive issues. To lower your risk of developing a deficiency, limit your alcohol intake, as this can make it hard for your body to absorb this nutrient. If you have a digestive condition or disease, follow your doctor’s instructions on care and management.

Health Solutions From Our Sponsors

Medically Reviewed on 7/29/2022

Cedars Sinai: "Vitamin B-12 Deficiency Anemia."

Cleveland Clinic: "Vitamin B12 Deficiency."

Harvard Health Publishing: "Vitamin 12 deficiency can be sneaky and harmful."

Harvard T.H. Chan: "Vitamin B12."

Johns Hopkins Medicine: "Vitamin B12 Deficiency Anemia."

Mayo Clinic: "Vitamin deficiency anemia."

Mount Sinai: "Vitamin B12 deficiency anemia."

NHS inform: "Vitamin B12 or folate deficiency anaemia."