Age  Recommended Amount
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  
Pregnancy   2.6 mcg  
Breastfeeding   2.8 mcg   
What Are the Symptoms of a Deficiency?

Vitamin B12 deficiency symptoms can vary. Some common signs of low B12 levels include:

Dizziness

Fatigue

Headaches

Jaundice (yellow eyes and skin)

Lower appetite

Nausea

Painful, smooth, red tongue

Rapid heart rate or shortness of breath

Tingling in hands and feet

Weight loss

Other symptoms can be uncontrolled muscle movement, vision changes, depression, poor memory, confusion, and mouth or tongue soreness.

Infants may refuse solid food, have developmental delays, and have signs of anemia.

Plant foods generally lack vitamin B12, but you can get it from animal foods like fish, meat, eggs, and poultry.

Foods high in vitamin B12 include:

Food Amount per Serving
Beef liver (3 ounces)   70.7 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 vegetarian or vegan, consider fortified cereals or nutritional yeast. B12 supplements might also be necessary. Talk to a doctor or registered dietitian to ensure you meet your needs.

Your body stores up to 2,000 times as much vitamin B12 as you eat daily. However, some people do not get enough through their diet. Others may have conditions that make it hard for the body to absorb it.

You may need B12 supplementation if you are in a high-risk group, such as:

A doctor may recommend B12 supplements by mouth to prevent deficiency if you do not get enough from food. There are two main forms: methylcobalamin (natural form) and cyanocobalamin (synthetic form).

In more severe cases, you may need B12 injections to ensure your body absorbs it effectively. You may switch to oral supplements once levels become normal, but some people need injections for life.

Vitamin B12 can be used sublingually (under your tongue) and nasally, but these are not well studied and may be expensive.

You may need 500-1,000 micrograms of vitamin B12 per day, as only a small percentage is absorbed.

Vitamin B12 is generally safe. In high doses, you may develop side effects like:

People who use B12 injections are more prone to allergic reactions.

Cyanocobalamin has an aluminum component that can worsen kidney function. People with kidney-related conditions should use methylcobalamin.

If you develop anemia due to a B12 deficiency, your complete blood count may take up to eight weeks to return to normal. More severe symptoms like memory problems, numbness, or tingling can take months to resolve.

Nerve damage due to untreated B12 deficiency may become permanent, especially in older adults.

Frequently Asked Questions

Edited by

Hannah Harper

Hannah Harper

Hannah Harper is a wellness editor for Health. Previously, she was an associate editor, assistant editor, and editorial assistant for Health. She covers topics on nutrition, women's health, and more.

learn more

Updated by

Emily Santora

Emily Santora

As a student at Arizona State University, Emily was a writer and editor for the Embryo Project Encyclopedia, where she researched, wrote, and published over 18 peer-reviewed encyclopedia articles. As a writer, Emily studied and wrote articles about the menstrual cycle.

learn more

Read more:

Was this page helpful?

Thanks for your feedback!

Tell us why!

11 Sources

Health.com uses only high-quality sources, including peer-reviewed studies, to support the facts within our articles. Read our editorial process to learn more about how we fact-check and keep our content accurate, reliable, and trustworthy.

National Institutes of Health: Office of Dietary Supplements. Vitamin B12 - health professional fact sheet. 

Leishear K, Boudreau RM, Studenski SA, et al. Relationship between vitamin B12 and sensory and motor peripheral nerve function in older adults. J Am Geriatr Soc. 2012;60(6):1057-1063. doi:10.1111/j.1532-5415.2012.03998.x

MedlinePlus. Vitamin B12. 

National Heart, Lung, and Blood Institute. Vitamin B12–deficiency anemia.

Ankar A, Kumar A. Vitamin B12 deficiency. In: StatPearls. StatPearls Publishing; 2024.

Dağ H, Koç MÖ, Dikker O, et al. Vitamin B12 serum levels of six to nine-month old infants according to feeding practices. J Pediatr Res. 2020;7(1):1-6. doi:10.4274/jpr.galenos.2019.00377

Wang H, Li L, Qin LL, Song Y, Vidal-Alaball J, Liu TH. Oral vitamin B12 versus intramuscular vitamin B12 for vitamin B12 deficiency. Cochrane Database Syst Rev. 2018;3(3):CD004655. doi:10.1002/14651858.CD004655.pub3

Al Amin ASM, Gupta V. Vitamin B12 (cobalamin). In: StatPearls. StatPearls Publishing; 2023.

Vasavada A, Patel P, Sanghavi DK. Cyanocobalamin. In: StatPearls. StatPearls Publishing; 2024.

MedlinePlus.Cyanocobalamin injection.

Langan RC, Goodbred AJ. Vitamin B12 deficiency: Recognition and management. Am Fam Physician. 2017;96(6):384-389.