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Vitamin B12, also known as cobalamin, is a water-soluble vitamin required for many body processes. It helps make red blood cells, create DNA and protein, and protect the nervous system.
The body can store several years’ worth of vitamin B12, making a deficiency harder to diagnose, as symptoms do not appear sooner. It is best to meet your vitamin B12 requirements daily rather than wait for symptoms to appear before using B12.
The recommended daily intake of vitamin B12 varies with age, sex, and other factors like pregnancy and lactation. The daily recommended dietary allowance (RDA) for vitamin B12 is as follows:
| Age | Recommended amounts |
| Birth to 6 months | 0.4 micrograms (mcg) |
| 7-12 months | 0.5 mcg |
| 1-3 years | 0.9 mcg |
| 4-8 years | 1.2 mcg |
| 9-13 years | 1.8 mcg |
| 14 years and older | 2.4 mcg |
| During pregnancy | 2.6 mcg |
| During lactation | 2.8 mcg |
The symptoms of vitamin B12 deficiency may vary across individuals, but can include:
- Nausea
- Numbing or tingling in the hands and feet
- Lower appetite
- Lack of energy (fatigue)
- Increased heart rate
- Weight loss
- Headaches
- Painful, smooth, red tongue
- Jaundice (yellowing of the eyes and skin)
- Dizziness
- Shortness of breath
Other symptoms of vitamin B12 deficiency may include uncontrollable muscle movement, vision problems, depression, poor memory, confusion, and soreness of the mouth or tongue.
Infants with B12 deficiency may refuse solid food, show developmental delays, and have anemia.
Vitamin B12 is generally not present in plant foods. You can get vitamin B12 from animal foods like fish, meat, eggs, and poultry. Foods high in vitamin B12 include beef liver, salmon, and eggs.
| Food | Amount per serving |
| Beef liver (3 ounces) | 70.7 micrograms (mcg) |
| Clams, without shells, cooked (3 ounces) | 17 mcg |
| Salmon (3 ounces) | 2.6 mcg |
| Egg, cooked (1 large) | 0.5 mcg |
| Turkey, breast meat, roasted (3 ounces) | 0.3 mcg |
| Milk, 2% milkfat (1 cup) | 1.3 mcg |
If you are a vegetarian or vegan, you can get vitamin B12 from fortified breakfast cereals and nutritional yeast. You may also need vitamin B12 supplements to meet your RDA. Consider talking to a healthcare provider or registered dietitian (RD) for recommendations to meet your daily nutrient needs.
Your body stores up to 2,000 times as much vitamin B12 as you eat daily. However, some people don’t get enough vitamin B12 through their diet. Other people may have health conditions that make it difficult for their bodies it.
People who may need B12 supplementation include:
- Older people
- People following a vegetarian or vegan diet
- People who underwent weight loss surgery (bariatric surgery)
- People with autoimmune diseases like Crohn’s or celiac disease
If you do not get enough vitamin B12 from food, your healthcare provider may recommend that you take B12 supplements by mouth to prevent the risk of deficiency. There are two main forms: methylcobalamin (natural form) and cyanocobalamin (synthetic form).
In more severe cases, your provider may recommend vitamin B12 injections: injecting the vitamin directly into the muscles to ensure the body absorbs it quickly and effectively. Depending on the cause of your deficiency, you may switch to oral supplements once your blood levels become normal. However, some people require B12 injections for life.
Vitamin B12 can be used sublingually (under the tongue) and nasally, but these routes have not been widely studied and may be expensive.
Healthcare providers generally prescribe about 500-1,000 micrograms of vitamin B12 per day to treat a deficiency. These doses seem significantly higher than the RDA of vitamin B12, but your body absorbs only a small percentage of them.
Vitamin B12 is generally safe. In high doses, you may experience side effects like:
- Pain at injection sites for people who use intramuscular (IM) vitamins
- Allergic reactions
- Fever
- Itching
- Rash
- Shortness of breath
- Rapid weight gain
People who use B12 injections are more prone to allergic reactions than those using oral medications. Cyanocobalamin also has an aluminum component that can worsen kidney function. For this reason, some experts recommend that people with kidney-related conditions use supplements containing methylcobalamin rather than cyanocobalamin.
If you develop anemia (a lack of red blood cells) due to a B12 deficiency, your complete blood count may take up to eight weeks to return to normal. More severe symptoms of neurological impairment, such as memory problems and numbness or tingling, can take months to resolve. Nerve damage due to untreated B12 deficiency may become permanent, especially in older people.
Vitamin B12 helps support nerve health and produce DNA and red blood cells. People following a vegetarian or vegan diet may require vitamin B12 supplements to meet their nutrient needs.
It may take time for vitamin B12 supplements to resolve a deficiency. In severe cases, your healthcare provider may recommend B12 injections. Recovery can take several weeks to months. If you have kidney problems, talk to your healthcare provider before using B12 supplements.
