Vitamin B-12 is an important vitamin for many bodily functions, such as brain health, blood cell production, and proper nerve functioning. There are several ways to test your B-12 levels. You can get your blood drawn or take a home urine test. These tests will look at the levels of your:

• overall vitamin B-12
• methylmalonic acid (MMA)
• homocysteine
• holotranscobalamin (holoTC)

Research suggests that MMATrusted Source and holoTCTrusted Source may be more accurate at reading low B-12 levels because they represent active B-12. Low B-12 levels can lead to:

• permanent nerve damage
• deteriorating brain functions
• memory loss
• temporary infertility in women

People who are obese or eat a lot of meat also tend to have higher-than-normal levels. High levels of vitamin B-12 can be a sign of liver disease, certain types of leukemia, or diabetes.

Vitamin B-12 deficiency is a common condition. Between 1.5 and 15 percent of Americans have low levels of vitamin B-12, according to the National Institutes of HealthTrusted Source. Many people, especially older adults and people with intestinal disorders, have trouble absorbing vitamin B-12 from food and oral supplements.

Potential Health Benefits

Given the vital roles that vitamin B12 plays in your body, a deficiency can have serious health consequences.

In fact, low blood levels of the vitamin have been linked to several health problems.

Brain Function

Low levels of vitamin B12 have been linked to a decline in brain function.

Two recent reviews found that there may be a link between low blood levels and the development of dementia (17Trusted Source, 18Trusted Source).

However, results have been mixed and treatment with vitamin B12 wasn’t effective at improving brain function in people with normal brain function (19Trusted Source, 20Trusted Source, 21Trusted Source).

Depression

It’s been suggested that there may be a link between low vitamin B12 levels and depression.

However, one review found that treating depression with vitamin B12 didn’t reduce the severity of symptoms.

Nevertheless, it was suggested that taking the vitamin on a long-term basis could help prevent a relapse into depression (22Trusted Source).

Currently, there is a lack of quality research in this area. Higher quality studies are needed to find out if there is a link between vitamin B12 and depression (23Trusted Source).

Osteoporosis

Osteoporosis is a disease in which the loss of bone mass results in weaker bones and an increased risk of bone fractures.

Interestingly, low blood levels of vitamin B12 have been linked with reduced bone mass (24Trusted Source).

Therefore, it’s been suggested that taking vitamin B12 may reduce your risk of osteoporosis. However, studies have provided mixed results (25Trusted Source, 26Trusted Source, 27Trusted Source).

Age-Related Macular Degeneration

Age-related macular degeneration is a condition that causes you to gradually lose central vision, usually in both eyes.

In people aged 50 and over, adequate consumption of vitamin B12 is thought to be important for maintaining good vision and protecting against macular degeneration.

How much vitamin B-12 do you need?

How much B-12 you need depends on your age and if you are pregnant or breastfeeding. The table below shows how much