Ulcerative colitis (UC) causes inflammation and ulcers on the intestinal lining. A person with UC may be unable to absorb certain nutrients, including vitamin B12.

UC is a form of inflammatory bowel disease (IBD) and affects 600,000–900,000 people in the United States.

This article discusses the potential link between UC and vitamin B12, signs of a deficiency, and how to get sufficient vitamin B12 into the diet.

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UC usually causes inflammation in the inner lining of the large intestine. Typically, other forms of IBD, such as Crohn’s disease, affect the small intestines where the absorption of vitamins occurs.

According to the Crohn’s and Colitis Foundation, people with UC tend to have fewer severe nutritional deficiencies than those with other forms of bowel disease.

B12 deficiency is more common in those with Crohn’s disease, but people with UC are also at risk. According to a 2015 study, the prevalence of B12 deficiency among individuals with Crohn’s disease was 33% compared with 16% of those with UC.

However, people with UC may still develop problems absorbing nutrients due to malnutrition and symptoms of this condition. If a person experiences severe diarrhea or blood in stool, it can lead to nutrient loss and further complications. For example, the loss of iron could cause iron anemia.

Some studies also suggest that levels of certain vitamins may play a role in developing IBD. For example, vitamin B12 and serum folate levels influence the development of IBD, such as UC.

Vitamin B12 promotes blood and nerve cell health and helps make DNA. Recognizing signs of a vitamin B12 deficiency is helpful before symptoms become serious.

According to the National Institutes of Health (NIH), signs of a vitamin B12 deficiency include:


Doctors diagnose a vitamin B12 deficiency through a blood test. A doctor may order routine blood tests on someone with UC to determine their baseline level and ensure they do not have a deficiency.

Future blood tests to continue to monitor B12 also help make sure a person maintains good vitamin levels even if they have a flare-up of UC symptoms.

Diet is the best way to prevent a vitamin B12 deficiency for someone with UC. Suitable sources of B12 include:

However, certain individuals may not be able to tolerate some of these foods. For example, red meat and dairy may worsen symptoms in those with IDB. Therefore, they may need to take supplements or consider other dietary options to maintain their levels of vitamin B12.

Learn more about B12 foods for vegetarians.

In addition, taking vitamin B12 supplements may help prevent a deficiency.

The recommended dose for vitamin B12 may vary depending on specific medical conditions and the disease severity. Generally, the recommended daily allowance for vitamin B12 for people ages 14 and over is 2.4 micrograms. However, this allowance is what the average adult needs to avoid deficiency, so they may need more to maintain optimal levels of vitamin B12.

Different brands and forms of vitamin B12 supplements may contain a varied amount of this nutrient. For example, vitamin B12 levels in a multivitamin may differ from supplements that contain vitamin B.

As with any supplement, an individual should speak with their doctor or healthcare professional before starting.

Another option is vitamin B12 shots. A shot of B12 is available via a prescription to treat vitamin B deficiencies. The injections bypass absorption barriers and can be suitable for people with a B12 deficiency.

People with UC may also develop other types of nutritional deficiencies. According to the Crohn’s and Colitis Foundation, individuals with this condition may want to consider the following supplements:

  • Calcium: This helps maintain strong teeth and bones. Taking medications, such as corticosteroids for inflammation, may weaken bones and increase the likelihood of osteoporosis. Calcium may help prevent low bone density.
  • Folate: Folic acid promotes new cell production and helps the body process fats. Some prescription IBD medications, such as sulfasalazine and methotrexate, may interfere with the absorption of folic acid.
  • Iron: The body needs adequate iron levels to maintain proper levels of hemoglobin, which helps carry oxygen through the body. A person with UC may be at risk of low iron levels due to reduced intake or absorption of iron in the diet and blood loss. Read on for the link between UC and anemia.
  • Vitamin D: Vitamin D helps the body absorb calcium, which promotes healthy and strong bones. Moderate levels of vitamin D may also help control disease activity. Vitamin D has anti-inflammatory properties, and low levels of this vitamin are more common in people with IBD.

UC can affect the body’s ability to absorb nutrients. Vitamin B12 plays a significant role in several body functions, including red blood cell production.

Without suitable levels of B12, symptoms of a deficiency, such as weakness, weight loss, and confusion, may occur in people with UC. A person can eat foods high in vitamin B12 or take a supplement to help prevent deficiency in vitamin B12.