What B12 does
Vitamin B12 helps your body make red blood cells and keep nerves healthy. It also helps copy DNA when cells divide. You cannot make it yourself. It comes from animal foods such as meat, fish, eggs, and dairy, or from fortified foods and supplements.
The liver stores a few years' worth of B12. That is why a deficiency builds slowly. Symptoms can take years to appear, and by then the cause may be well established.
Signs you might be low
The early signs are vague. People feel tired, weak, and short of breath with light effort. Skin can look pale or slightly yellow. The tongue may become smooth and sore.
Nerve symptoms come next. Tingling or numbness in the hands and feet is common. Balance can get worse, especially in the dark. Memory and concentration slip. Mood can drop. In older adults, this is sometimes mistaken for dementia.
Nerve damage from long-term deficiency can become permanent. That is why early testing matters.
Who is most at risk
People who eat no animal products are at high risk unless they supplement. Adults over 60 absorb less B12 because stomach acid falls with age. People who have had weight-loss surgery or who have Crohn's or celiac disease absorb less too.
Two common medications lower B12 over time. Metformin, the diabetes drug, is one. Acid-reducing drugs such as omeprazole are the other. Anyone on these for years should get checked.
Pernicious anemia is an autoimmune condition. The body attacks the stomach cells that make a protein needed to absorb B12. People with this condition need B12 injections or very high oral doses for life.
How it is diagnosed
A blood test measures total B12. Levels below about 200 pg/mL are clearly low. Levels between 200 and 300 are a gray zone. In that range, doctors add a second test called methylmalonic acid, or MMA. High MMA confirms the body is short on usable B12 even if the first number looks borderline.
A complete blood count may show large red blood cells, which is a classic sign. Zen IV Spa can send a nurse to your home in New York and New Jersey to draw these labs. The first video visit with the medical director is free.
How it is treated
If the gut can absorb B12, high-dose oral tablets work well. A randomized trial in older adults found that 1,000 to 2,000 micrograms a day by mouth raised levels as well as injections did. The dose is far above the daily requirement because only a small fraction gets absorbed.
If absorption is the problem, injections bypass the gut entirely. A typical plan is a series of shots over a few weeks, then one a month. Symptoms like fatigue often improve within days to weeks. Nerve symptoms take longer and may not fully reverse if they were present for a long time.
IV vitamin blends also contain B12. The Myers' cocktail at Zen IV Spa, $299, includes B vitamins, vitamin C, and magnesium, and the nurse can add a B12 shot. These are wellness services and are not a substitute for treating a diagnosed deficiency, but they can be part of the plan the medical director sets.
Preventing it
Eat B12-rich foods regularly, or take a daily supplement of at least 2.4 micrograms if you avoid animal products. Over 50, a supplement or fortified cereal is a sensible habit. If you take metformin or an acid reducer long term, ask for a B12 level once a year.
Where to start with Zen IV Spa
If you have been tired or foggy and want a real answer, visit /everyday-health/ to book a free video visit. A nurse can draw labs at home, and the medical director can prescribe B12 or an everyday prescription for $79 a month if needed. Call (332) 239-2005 with questions.
Common Questions
Can B12 deficiency cause anxiety or depression?+
Yes. Low B12 is linked to mood changes, and correcting it sometimes helps. It is worth testing before assuming the cause is purely psychological.
How long does it take to feel better after treatment?+
Energy often improves within one to two weeks. Nerve symptoms can take three to six months and may not fully resolve if they were long-standing.
Is a B12 shot better than a pill?+
For most people with a working gut, high-dose pills work just as well. Shots are the right choice when absorption is poor, such as in pernicious anemia or after stomach surgery.
Can you take too much B12?+
B12 has no set upper limit because the body excretes the excess in urine. Very high doses are considered safe, though they are not useful if you are not low.
Does a normal B12 level rule out a deficiency?+
Not always. A borderline level with symptoms should be followed up with a methylmalonic acid test, which is more sensitive.
Sources: NIH Office of Dietary Supplements fact sheet on vitamin B12 (2024); randomized trial of oral versus intramuscular B12 (Blood, 1998; Cochrane review 2018); Mayo Clinic patient information on vitamin deficiency anemia; American Family Physician review on B12 deficiency (2017).
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.
