Vitamin B12 and Nerve Function: What the Science Says

What Is Vitamin B12?

Vitamin B12 is a water-soluble vitamin naturally present in foods of animal origin and added to some fortified foods. It is also available in dietary supplements and, in certain situations, as a prescription medication.

The body needs vitamin B12 for healthy red blood cell formation, DNA synthesis and normal development and function of the nervous system.

Why Is Vitamin B12 Important for Nerves?

According to the National Institutes of Health Office of Dietary Supplements, vitamin B12 is required for the development, myelination and function of the central nervous system.

Myelin is part of the protective structure surrounding many nerve fibers. Maintaining normal neurological function therefore depends, among many other factors, on adequate vitamin B12 status.

Can Vitamin B12 Deficiency Cause Tingling or Numbness?

Yes. Vitamin B12 deficiency can produce neurological changes, including numbness and tingling in the hands and feet.

Importantly, neurological symptoms can occur even when the classic anemia associated with B12 deficiency is not present.

For broader information about these sensations, see our guides to Tingling Feet at Night and Foot Numbness.

Who May Be More Likely to Have Inadequate B12?

Low B12 status is not always caused simply by eating too little of the vitamin. Absorption is an important part of the picture.

Groups that may be at greater risk include:

• Some older adults
• People with pernicious anemia
• People with certain gastrointestinal disorders
• People who have undergone some types of gastrointestinal surgery
• People following vegetarian or vegan diets without adequate B12 sources
• People using certain medications that can affect B12 status

What Foods Contain Vitamin B12?

Vitamin B12 occurs naturally in foods of animal origin. Examples include:

• Fish and seafood
• Meat
• Poultry
• Eggs
• Milk and other dairy products

Plant foods do not naturally contain vitamin B12, although some foods, such as certain breakfast cereals and nutritional yeasts, are fortified with it.

How Much Vitamin B12 Do Adults Need?

The U.S. Recommended Dietary Allowance for most adults is 2.4 micrograms (mcg) per day. Requirements are higher during pregnancy and breastfeeding.

This recommended dietary amount should not be confused with the much larger doses often found in B12 supplements.

Why Do Some B12 Supplements Contain Such Large Amounts?

Vitamin B12 supplements can contain doses far above the daily recommended intake. One reason is that the percentage of B12 absorbed decreases substantially at high supplemental doses.

A large number on a supplement label therefore does not mean the body absorbs that entire amount, nor does a higher dose automatically mean a better outcome.

Methylcobalamin vs. Cyanocobalamin: Is One Better?

Vitamin B12 supplements are available in several forms, including cyanocobalamin and methylcobalamin.

According to the NIH Office of Dietary Supplements, available evidence does not indicate that absorption rates of supplemental vitamin B12 differ by form.

Marketing claims suggesting that one form is universally superior should therefore be evaluated separately from what clinical evidence actually demonstrates.

Does Taking B12 Improve Nerve Symptoms?

This question requires an important distinction.

When neurological symptoms are related to an actual vitamin B12 deficiency, identifying and appropriately treating that deficiency is medically important.

But the presence of tingling, burning or numbness does not by itself show that B12 is low. These symptoms have many possible causes.

Therefore, the evidence that B12 is essential for normal nerve function should not be interpreted as evidence that taking B12 supplements will improve every type of nerve symptom in people who already have adequate B12 status.

How Is Vitamin B12 Status Evaluated?

Healthcare professionals commonly use blood testing to evaluate vitamin B12 status. Serum or plasma B12 is often measured, and additional markers such as methylmalonic acid may sometimes be used when results require further clarification.

Test interpretation depends on the individual situation and should be discussed with a qualified healthcare professional.

Can Medications Affect Vitamin B12?

Yes. Certain medications can affect vitamin B12 status. The NIH notes, for example, that prolonged use of some gastric acid inhibitors and metformin can reduce B12 absorption or blood concentrations in some people.

People taking medications regularly should not stop or change them because of information read online. Questions about B12 status and medication use should be discussed with the prescribing healthcare professional.

What Should You Look for in a “Nerve Support” Supplement?

Vitamin B12 frequently appears in products marketed for nerve support. Seeing B12 on a label tells you that the product contains a nutrient required for normal nervous-system function. It does not, by itself, demonstrate that the finished supplement treats neuropathy or relieves nerve symptoms.

Useful questions include the form of B12 used, the amount provided, what other ingredients are present and what evidence supports the claims being made for the finished product.

We will examine these questions separately in our upcoming guide to evaluating nerve-support supplement ingredients.