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- Vitamin B12 deficiency causes symptoms like fatigue, sore tongue, constipation, and confusion.
- B12 deficiency is caused by a lack of dietary B12 or pernicious anemia, which affects B12 absorption.
- To treat a B12 deficiency, you may need to get B12 injections or take a supplement.
- Visit Insider's Health Reference library for more advice.
Vitamin B12 is a water-soluble vitamin that plays an essential role in many bodily functions, like red blood cell formation and nerve function. It can be found in foods like beef, fish, and eggs. But, despite the vitamin's importance, between 1.5% and 15% of the general US population is deficient in B12.
A B12 deficiency can cause symptoms like fatigue and constipation and could even lead to permanent neurological damage if left untreated. Here is how to recognize a B12 deficiency, its potential causes, and treatment options.
Vitamin B12 deficiency symptoms
Symptoms of a B12 deficiency can develop over time or come on suddenly, says Kailey Proctor, a board-certified oncology dietitian at the Leonard Clinical Cancer Institute with Mission Hospital. Symptoms can also vary depending on the severity of the deficiency.
Signs of a mild B12 deficiency include:
- A yellow tinge to the skin
- Irritability
- Fatigue
- Canker sores
- Sore and swollen tongue
- Difficulty with balance
- Constipation
- Loss of appetite
- Numbness and tingling in hands and feet
- Confusion and poor memory
The longer a B12 deficiency is left untreated, the more severe and potentially irreversible symptoms will become, says Elizabeth Beil, a registered dietitian and founder of Elizabeth Beil Nutrition.
Signs of a severe B12 deficiency include:
- Paralysis
- Neurological complications, like an unsteady gait or difficulty walking
- Depression
- Dementia
What causes b12 deficiency
Causes of B12 deficiency include:
- A lack of vitamin B12 in the diet
- Gastrointestinal disorders that interfere with vitamin B12 absorption, like Crohn's or celiac disease.
- Pernicious anemia, a specific kind of anemia that occurs when the body cannot absorb enough B12. People with this condition lack a type of protein made in the stomach called intrinsic factor, which is needed to absorb vitamin B12.
Some medications can also interfere with B12 absorption and cause a deficiency, including:
- Metformin, which is used to treat type 2 diabetes.
- Chloramphenicol, which is an antibiotic generally used to treat eye and ear infections.
- Proton pump inhibitors, like Prilosec and Prevacid, used to treat acid reflux.
- H2 receptor antagonists, like Pepcid and Zantac.
Diagnosis
If your doctor suspects you may have a B12 deficiency, they can do a lab test to check B12 levels in your blood:
- A normal serum B12 level is between 300 pg/mL and 900 pg/mL
- Between 200 to 300 is considered borderline
- Levels below 200 are considered low and consistent with B12 deficiency.
Vitamin B12 deficiency treatment
Treatment of B12 deficiency generally depends on the severity of the deficiency and what is causing it, Proctor says. Treatment options include:
- B12 injections Dosage and frequency of injections can vary, but general guidelines are three injections a week for two weeks, though some people who are not able to adequately absorb vitamin B12 may need to get regular injections every one to three months. It's important to note that B12 injections can lead to side effects like dizziness and headaches.
- B12 supplements in the form of oral or sublingual tablets that dissolve under the tongue are an over-the-counter treatment option for people who lack B12 in their diets, like vegans or vegetarians, Beil says.
- Increasing intake of foods with B12, like:
- Milk, which contains 1.2 micrograms per cup
- Eggs, which contain 0.6 micrograms per serving
- Salmon, which contains 4.8 micrograms per 3 ounces
- Cheese, which contains 0.9 micrograms per ounce
The fastest way to raise B12 levels is by receiving injections. Those taking supplements or increasing their consumption of B12 foods should see an improvement in symptoms within six to 12 months, Beil says.
Insider's takeaway
A vitamin B12 deficiency can be caused by a gastrointestinal disorder or a lack of B12 in your diet. Signs of a B12 deficiency include weakness, fatigue, and tingling or numbness in the hands and feet. Symptoms are reversible if adequately treated early on with B12 injections or dietary supplementation.