Vitamin B12 After 40: Who Needs to Pay Attention and Why

Vitamin B12 is one of those nutrients most people never think about until something goes wrong. Yet deficiency is more common than many realize, especially as we age, and its early symptoms are easy to mistake for stress, poor sleep or simply getting older.

This guide explains what B12 does, why your risk rises after 40 and 50, and what to do about it.

What vitamin B12 does

Vitamin B12 is essential for:

• Making healthy red blood cells
• Keeping nerve cells healthy
• Making DNA, the genetic material in all cells
• Supporting normal brain function

According to the NIH Office of Dietary Supplements, adults need 2.4 micrograms (mcg) of vitamin B12 a day. Needs are slightly higher during pregnancy and breastfeeding.

How your body absorbs B12

B12 absorption is a surprisingly complicated process. In food, B12 is attached to protein. Stomach acid and enzymes release it, and then it must bind to a protein called intrinsic factor, made by the stomach, before it can be absorbed in the small intestine.

Problems at any step can lead to deficiency, which explains why some people run low even when they eat plenty of B12-rich foods.

Who is at higher risk?

The Office of Dietary Supplements identifies several groups at higher risk of deficiency:

Older adults

Many older adults have atrophic gastritis, a condition in which the stomach makes less acid. With less acid, the body has more trouble releasing B12 from food. For this reason, the ODS notes that adults over 50 should get much of their B12 from fortified foods or supplements, because that form is not bound to protein and is easier to absorb. The Dietary Guidelines for Americans make a similar point.

People taking certain medications

• Metformin, a common diabetes medication, can reduce B12 absorption with long-term use.
• Proton pump inhibitors (such as omeprazole) and H2 blockers (such as famotidine), used for heartburn and reflux, reduce stomach acid and may lower B12 absorption over time.

If you take these regularly, ask your clinician whether periodic B12 testing makes sense. Do not stop a prescribed medication on your own.

People with pernicious anemia

Pernicious anemia is an autoimmune condition in which the body cannot make intrinsic factor, so B12 cannot be absorbed from food. It is more common in older adults and requires medical treatment, often B12 injections or high-dose supplements.

People with digestive conditions or surgery

Celiac disease, Crohn's disease and weight-loss surgery can all affect B12 absorption.

People who eat little or no animal food

B12 is found naturally only in animal foods. Vegans, and some vegetarians, need fortified foods or supplements to get enough.

Symptoms of B12 deficiency

B12 deficiency usually develops slowly, over months or years, because the body stores a fair amount in the liver. Symptoms can include:

• Tiredness, weakness and low energy
• Pale skin
• Shortness of breath
• Numbness or tingling in the hands and feet
• Problems with balance or walking
• A sore, smooth or red tongue
• Memory problems, confusion or difficulty concentrating
• Low mood or irritability

Some of these, particularly nerve symptoms, can become permanent if deficiency goes untreated for a long time. That is a good reason not to ignore persistent tingling, balance problems or memory changes.

Many of these symptoms overlap with other conditions common in midlife, which is why testing matters. Mayo Clinic lists anemia and vitamin deficiencies among the many possible causes of fatigue.

Food sources of vitamin B12

Good sources include:

If you are over 50, take acid-reducing medication or metformin, or eat few animal foods, fortified foods are particularly useful because their B12 does not depend on stomach acid to be released.

Testing for B12 deficiency

A blood test can measure your B12 level. Because results near the low end of normal can be hard to interpret, clinicians sometimes order additional tests, such as methylmalonic acid (MMA), to clarify. A complete blood count can show the large red blood cells typical of B12 or folate deficiency, though B12 deficiency can also affect nerves before it causes anemia.

It is reasonable to ask about B12 testing if you:

• Are over 50 and have symptoms like fatigue, tingling or memory changes
• Have taken metformin or acid reducers for a long time
• Follow a vegan diet
• Have had weight-loss surgery or have a digestive condition

Supplements: what to know

If you are low, your clinician will recommend a treatment plan. Options include oral supplements and, in some cases, injections, particularly for pernicious anemia or severe deficiency.

The Office of Dietary Supplements notes that B12 has a low potential for harm, and no upper limit has been set. However, it is still wise to:

• Test first rather than guess, because symptoms overlap with many other conditions
• Tell your clinician about all supplements you take
• Be wary of products that promise "energy boosts." B12 only improves energy if you are actually deficient

The ODS guide to dietary supplements and NCCIH's advice on using supplements wisely are good general primers.

The bottom line

Vitamin B12 deficiency becomes more likely with age, with certain common medications and with plant-only diets. Because it develops slowly and its symptoms are vague, it is easy to miss. If you are in a higher-risk group or have symptoms like fatigue, tingling or memory changes, ask your clinician about a simple blood test. Fortified foods are an easy way to get B12 after 50.

Frequently asked questions

How do I know if I need a B12 supplement?

The best way is a blood test ordered by your clinician, especially if you are over 50, take metformin or acid reducers, follow a vegan diet or have symptoms like fatigue or tingling.

Can low B12 cause tiredness?

Yes. B12 deficiency can cause fatigue and weakness, often along with other symptoms like tingling, a sore tongue or memory problems. But fatigue has many causes, so testing is important.

Is it safe to take B12 every day?

The NIH Office of Dietary Supplements notes vitamin B12 has a low potential for harm and no upper limit has been set. Still, check with your clinician, especially if you take other medications.

Does metformin really lower B12?

Long-term metformin use is associated with lower B12 levels in some people. If you take it, ask your clinician whether periodic testing is appropriate.