What vitamin B12 is
Vitamin B12 is also called cobalamin. It is a water-soluble vitamin, which means your body does not store it the way it stores fat-soluble vitamins. The liver does hold a reserve, often enough for a few years, which is why a deficiency can creep up slowly.
Your body uses B12 for three big jobs. It helps make red blood cells. It keeps the coating around your nerves healthy. And it helps build DNA. B12 also works hand in hand with folate, another B vitamin, so a problem with one often affects the other.
Adults need about 2.4 micrograms a day. That is a tiny amount, and most people who eat meat, fish, eggs, or dairy get enough. B12 is only found naturally in animal foods. Plants do not make it.
Why people run low
The biggest risk group is people who eat a vegan or mostly plant-based diet. Without animal foods or a supplement, the body slowly uses up its reserve.
The second group is people who cannot absorb it well. B12 absorption is tricky. Stomach acid frees it from food, then a protein called intrinsic factor carries it into the small intestine. Anything that interferes with that chain causes problems. Older adults make less stomach acid. People with pernicious anemia, an autoimmune condition, do not make intrinsic factor. Gastric bypass surgery, celiac disease, and Crohn's disease also reduce absorption.
Common medicines matter too. Metformin, the most-prescribed diabetes drug, lowers B12 in a large share of long-term users. Acid-reducing drugs like omeprazole and famotidine, taken for years, do the same. Heavy alcohol use is another cause.
Signs of B12 deficiency
The early signs overlap with many other things. Fatigue, weakness, and shortness of breath come from anemia. A smooth, sore tongue and loss of appetite are common.
The nerve symptoms are what make B12 special and serious. Numbness or tingling in the hands and feet, trouble with balance, and a feeling of walking on cotton are classic. Memory problems, confusion, low mood, and irritability can show up as well. In older adults, B12 deficiency is sometimes mistaken for dementia.
Nerve damage from B12 deficiency can become permanent if it goes untreated for too long. That is why it is worth testing early rather than waiting.
How it is tested
A blood test for serum B12 is the usual first step. A level under about 200 picograms per milliliter is low. Levels between 200 and 300 are a gray zone. In that case, a second test called methylmalonic acid, or MMA, helps. MMA rises when cells are starving for B12 even if the blood level looks borderline.
A complete blood count shows whether red cells are oversized, a sign of B12 or folate anemia. Folate is usually checked at the same time, because the two deficiencies look alike and treating one without the other can cause problems.
How it is treated
If the problem is diet, a daily oral supplement works well. Doses of 500 to 1,000 micrograms a day are common. That sounds huge compared with the 2.4 microgram daily need, but only a small fraction is absorbed without intrinsic factor, so the high dose compensates.
If the problem is absorption, such as pernicious anemia or gastric surgery, B12 injections skip the gut entirely. A typical plan is injections every few days at first, then once a month. High-dose oral B12 can also work for many people with absorption problems, and a clinician can help decide.
B12 is very safe. There is no set upper limit because the body simply passes extra out in urine. Energy and blood counts usually improve within a few weeks. Nerve symptoms take longer and may not fully reverse if damage was severe.
How Zen IV Spa can help
Zen IV Spa serves New York and New Jersey. A licensed nurse can draw your B12, folate, MMA, and a blood count at home, and our medical team reviews them on a free video visit. If you are low, our everyday prescriptions program, $79 a month, can cover ongoing treatment. For a faster lift, our Myers' cocktail IV, $299, delivers B12 and the other B vitamins straight into your bloodstream, and the Mega Myers', $399, adds more. See the options at /everyday-health/ or call (332) 239-2005.
Common Questions
What does vitamin B12 do?+
It helps make red blood cells, protects nerves, and builds DNA. Running low causes anemia and nerve damage.
Who is most at risk of low B12?+
Vegans, adults over 50, people on metformin or long-term acid reducers, and people with pernicious anemia, celiac disease, or past stomach surgery.
What are the symptoms of B12 deficiency?+
Fatigue, shortness of breath, a sore tongue, numbness or tingling in hands and feet, balance problems, and memory or mood changes.
Can you take too much B12?+
There is no set upper limit. Extra is passed out in urine. Very high doses are considered safe.
Are B12 shots better than pills?+
Shots are best when the gut cannot absorb B12. For dietary deficiency, high-dose pills usually work just as well.
How quickly will I feel better?+
Energy and blood counts often improve within a few weeks. Nerve symptoms can take months, and severe damage may not fully reverse.
Sources: NIH Office of Dietary Supplements, Vitamin B12 Fact Sheet for Health Professionals, 2024; Mayo Clinic, Vitamin B12; Cleveland Clinic, Vitamin B12 Deficiency; Aroda et al., metformin and B12 deficiency in the Diabetes Prevention Program, Journal of Clinical Endocrinology and Metabolism, 2016.
All treatments are medical services. Every guest is screened, and every treatment is prescribed by a licensed provider. Nothing on this page is medical advice for you personally, and the opinions summarized here belong to the doctors named, not to Zen IV Spa. Talk to a provider before starting or stopping anything.
