Vitamin B12 helps in the creation of red blood cells, which deliver oxygen to cells throughout your body. B12 also helps to maintain the nervous system and participates in metabolism, which is the breakdown of carbohydrates, protein and fat to provide energy to operate, maintain and repair your body.
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When you have a vitamin B12 deficiency, you feel tired and weak. Some people develop skin rashes from vitamin B12 deficiency. Ironically, skin rashes can also occur as a response to supplement treatment for B12 deficiency.
Read more: The Best Way to Take Vitamin B12 Supplements
Why Supplements Are Necessary
Most people obtain sufficient vitamin B12 from the food they eat, including shellfish, fish, beef, lamb, cheese and eggs. Deficiencies may occur if you're missing a protein called intrinsic factor that helps you absorb vitamin B12.
Additionally, several conditions may lead to problems with absorbing vitamin B12, such as pernicious anemia, gastric bypass surgery, celiac disease, bacteria growth in the small intestine and Crohn's disease.
People are more prone to develop vitamin B12 deficiencies as they age. Heavy alcohol consumption and certain drugs can also disrupt B12 absorption as well.
Vegetarians usually get sufficient B12 from dairy foods, but vegans — those who abstain from eating all animal products — must take supplements to meet their B12 needs.
Read more: Foods High in B Vitamins
Symptoms of B12 Deficiency
Symptoms that may indicate you need supplemental vitamin B12 may include fatigue, pale skin, sore tongue, bleeding gums, weight loss, diarrhea, constipation, numbness or tingling in fingers and toes, balance problems, depression, loss of mental abilities and, for some people, skin rashes.
If a B12 deficiency is suspected, your physician can do a blood test to evaluate your levels of B12 and likely other B vitamins, including folic acid.
Treatment of B12 Deficiency
Often, doctors treat anemia through injections of hydroxo-B12, methyl B12 or cyano B12. Shots are typically given daily for a week, then once a week for a month, then monthly. You can learn how to give yourself shots, or a family member can learn how to administer the shots.
If the anemia is not too severe, your doctor may prescribe oral, sublingual — which means under the tongue — or nasal forms of B12 supplements. In any case, you usually cannot take too much B12. Your body absorbs what it can use, stores it in your liver and excretes the excess.
Side effects of B12 supplements are rare, according to the Southern Cross Healthcare Group, and generally occur with injections and not with oral supplements. Vitamin B12 side effects may include pain at the injection site, dizziness, diarrhea, nausea, headache, vomiting, acne and skin rash.
People with a B12 allergy may have hypersensitive responses to the injection. Allergic responses can include shortness of breath, swelling of the face, lips, tongue or other body parts, and rashes, hives or itching. Some people have immediate responses to an injection, but for others, it can take from several days to several weeks of injections for an allergic response to appear.
Read more: The Side Effects of Too Much Vitamin B12
If You Get a Rash
If you develop rashes, hives or other skin condition in response to B12 shots, speak with your doctor immediately. You may have hypersensitivity, and you will likely continue to have adverse responses as long as you continue injections.
If you're hypersensitive, your doctor may choose to have you try sublingual, nasal or oral forms of B12. If you discontinue B12 injections, it may take as long as four months for your rash to clear up.
Caution With a B12 Rash
If your skin turns red during vitamin B12 supplementation, you may be prone to developing photosensitivity, which is unusual sensitivity to sunlight or artificial UV rays. Avoid going out in the sun, or wear sunscreen and protective clothing if you do go out. Speak with your doctor regarding your side effects.