Vitamin B12 Deficiency Signs and Who Needs Supplements

9 min read

Last updated November 10, 2026

Common signs of vitamin B12 deficiency include tiredness, weakness and pale skin. Numbness, tingling and memory problems can also appear. Because the body stores B12, symptoms can take years to appear.

Older adults, vegans, people with certain stomach conditions and people who take metformin or acid reducers face a higher risk. A blood test can check your level.

This guide explains the signs of low B12, who is at risk and how deficiency is treated. It also covers the best food sources.

Health note. This article shares general information, not medical advice. Talk with your doctor before starting B12 supplements, and do not ignore numbness, tingling or memory changes.

Key Takeaways

Adults need 2.4 micrograms of vitamin B12 a day.
Plant foods have no B12 unless they are fortified.
Deficiency can cause anemia and nerve damage.
Older adults, vegans and people on metformin are at higher risk.
Nerve damage may become permanent if treatment is delayed.

Jump to a section

Why B12 matters
Signs of deficiency
Who is at risk
Medicines that lower B12
Food sources
Vegans and vegetarians
Testing
Treatment
When to get help
Frequently asked questions

Why Vitamin B12 Matters

Vitamin B12 helps your body make red blood cells and keeps nerves healthy. It also helps make DNA, the genetic material in every cell.

MedlinePlus explains that your body needs a protein called intrinsic factor to absorb B12. This protein is made in the stomach.

Problems with the stomach or intestines can block B12 absorption even when you eat enough. That is why some people need shots instead of food alone.

2.4 mcgDaily vitamin B12 recommended for adults, according to the NIH Office of Dietary Supplements.

Signs of Vitamin B12 Deficiency

Type	Possible signs
Blood	Tiredness, weakness, pale skin, fast heartbeat
Nerves	Numbness or tingling in hands and feet, balance problems
Brain and mood	Depression, confusion, poor memory
Mouth and gut	Sore or red tongue, loss of appetite, weight loss

These signs come from the NIH Office of Dietary Supplements. Many of them can also have other causes, so testing matters.

ODS warns that B12 deficiency can damage the nervous system even in people who do not have anemia. Do not wait for anemia before getting checked.

Quick tip. Keep a short list of symptoms and when they started. It helps your doctor decide which tests to order.

Why Symptoms Can Be Slow

ODS notes that your body stores a large amount of B12. Symptoms can take years to show up after intake or absorption drops.

This slow start means people may blame tiredness or forgetfulness on aging or stress. A simple blood test can rule B12 in or out.

People who stopped eating animal foods years ago may only now notice symptoms. The same is true for people who started metformin or acid reducers long ago.

If you fall into a risk group, regular testing can catch a problem before symptoms start. Ask your doctor how often you should be checked.

Have you ever had your vitamin B12 level checked?

Yes
No
I am not sure
Not sure what it is

Who Is at Risk

Adults over 50
People with pernicious anemia
People who had stomach or intestinal surgery
People with Crohn’s disease or celiac disease
Vegans and some vegetarians
People who take metformin or acid-reducing medicines

Harvard estimates that 10 to 30 percent of adults over 50 have trouble absorbing B12 from food. Low stomach acid is a common reason.

ODS advises people over 50 to get most of their B12 from fortified foods or supplements. These forms are easier to absorb.

What Is Pernicious Anemia?

Pernicious anemia happens when the body cannot make enough intrinsic factor. Without it, B12 from food cannot be absorbed well.

MedlinePlus explains that people with conditions like this often need B12 shots. Some need them for life.

Pernicious anemia is an autoimmune condition, which means the immune system attacks healthy cells in the stomach. It often runs in families.

People with other autoimmune conditions, such as thyroid disease or type 1 diabetes, may have a higher chance of pernicious anemia. Tell your doctor about your family history.

With regular treatment, most people with pernicious anemia live full, healthy lives. Staying on schedule with shots or pills is the key to staying in good health.

Medicines That Can Lower B12

Medicine	Why it matters
Metformin	May reduce B12 absorption
Proton pump inhibitors	May reduce B12 absorption from food
H2 blockers	May reduce B12 absorption from food

ODS says metformin might reduce B12 absorption and lower blood levels. Harvard adds that long-term metformin use is strongly associated with B12 deficiency.

Read more in our guide to metformin side effects. Ask your doctor whether you need regular B12 checks.

Many people take acid reducers for heartburn. Our guide to heartburn relief covers options to discuss with your doctor.

Best Food Sources of B12

Food group	Examples
Shellfish	Clams, oysters
Meat and organ meats	Beef, beef liver
Fish	Salmon, tuna, trout
Eggs and dairy	Milk, yogurt, cheese, eggs
Fortified foods	Some cereals, nutritional yeast, plant milks

ODS lists clams, oysters and beef liver among the best sources. It also notes that plant foods have no B12 unless fortified.

Harvard says nori seaweed contains too little B12 to rely on. Mushrooms are not a reliable source either, as our mushroom nutrition guide explains.

Vegans and Vegetarians

Harvard warns that people who do not eat meat, fish, poultry or dairy are at risk of B12 deficiency. Fortified foods or a supplement are recommended.

Choose fortified plant milks and cereals.
Use fortified nutritional yeast.
Ask your doctor about a B12 supplement.
Get your B12 level checked regularly.

Vegetarians who eat eggs and dairy get some B12, but intake may still be low. Iron is another nutrient to watch, as covered in our guide to iron rich vegetables.

Pregnancy and Breastfeeding

ODS says pregnant women need slightly more B12, and breastfeeding women need a bit more still. Harvard notes that the baby needs B12 for brain and nerve development.

Pregnant vegans and vegetarians should talk with their doctor about B12. ODS warns that infants with low B12 may fail to thrive and reach milestones late.

Other Causes of Low B12

MedlinePlus lists several other causes of B12 deficiency. Some are surprising.

Heavy alcohol use
Long-term use of heartburn medicines
Misuse of nitrous oxide, sometimes called whippets
Poor nutrition during pregnancy
Poor diet in infants

Nitrous oxide misuse can quickly lead to serious nerve problems linked to B12. Anyone with new numbness after using it should see a doctor right away.

A Sample B12-Rich Day

Meal	Idea
Breakfast	Fortified cereal with milk or fortified plant milk
Lunch	Tuna or salmon salad sandwich
Snack	Yogurt or a hard-boiled egg
Dinner	Lean beef or chicken with vegetables

For vegans, swap in fortified plant milk, fortified cereal and nutritional yeast. A supplement may still be needed, so ask your doctor or a dietitian what fits your eating plan.

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Myths About Vitamin B12

Myth	Fact
B12 shots give everyone energy	They help mainly if you are low
Plant foods contain B12	Only fortified plant foods do
Normal blood count means normal B12	Nerve damage can happen without anemia
Only vegans get low B12	Older adults and some medicine users are at risk too

B12 shots or pills will not boost energy in people with normal levels. Testing first avoids wasted money and missed causes of tiredness.

B12 and Older Adults

Memory problems and confusion in older adults are sometimes blamed only on aging. Low B12 is one treatable cause worth checking.

Older adults also take more medicines, including metformin and acid reducers. Regular checkups help catch low B12 early.

Depression can also be linked to low B12. If mood changes appear, ask your doctor about testing. Learn about treatment options in our guide to SSRI antidepressants.

How B12 Deficiency Is Tested

MedlinePlus lists several blood tests doctors may use, including a complete blood count and a serum B12 level. Methylmalonic acid and homocysteine tests may also help.

Harvard notes that a standard B12 blood test can miss some deficiencies. Methylmalonic acid and homocysteine are often better markers.

Doctors may also test for antibodies linked to pernicious anemia. Low iron can cause similar tiredness, so your doctor may check that too. See our iron supplements guide.

How Deficiency Is Treated

MedlinePlus explains that treatment depends on the cause. If diet is the cause, B12 pills may fix the problem.

When a health condition blocks absorption, treatment may include B12 shots, often monthly at first. Some people do well with high-dose pills, and a nasal spray form also exists.

Your doctor will choose the right form and schedule. Do not self-treat nerve symptoms without a diagnosis.

Choosing a B12 Supplement

B12 supplements come as pills, chewables, liquids and sublingual tablets that dissolve under the tongue. Many multivitamins also contain B12.

Ask your doctor whether you need a supplement.
Look for third-party testing seals on the label.
Check the label for other added vitamins.
Tell your pharmacist about all your medicines.

No supplement replaces medical care for nerve symptoms. Testing tells you and your doctor what you actually need.

Supplements are not reviewed for effectiveness before they reach stores. See supplement quality tips in our guide on collagen supplements. Our Drug Facts guide explains labels.

Is Too Much B12 Harmful?

ODS says vitamin B12 has not been shown to cause harm, even at high doses. Your body absorbs only a small part of large supplement amounts.

Still, check with your doctor before starting any supplement. Tell your pharmacist about all supplements and medicines you take.

Recovery and Outlook

MedlinePlus says people with B12 deficiency anemia often do well with treatment. The condition usually improves once the cause is treated.

Nerve damage is the main long-term risk. MedlinePlus warns it may be permanent if treatment does not start promptly after symptoms begin.

When to Get Help

Numbness or tingling in your hands or feet
Trouble with balance or walking
Memory loss or confusion
Ongoing tiredness, weakness or shortness of breath
A sore, red, swollen tongue

See a doctor soon for these symptoms. Call 911 for chest pain, severe shortness of breath or sudden confusion.

Your B12 Checklist

Know your risk factors
Eat B12 foods or fortified foods
Ask about testing if you take metformin
Watch for numbness or tingling
Talk to your doctor before supplements
Do not delay treatment for nerve symptoms

Try this today. Check the labels of your cereal or plant milk to see if they are fortified with vitamin B12.

Test Yourself

Which group is more likely to have trouble absorbing B12 from food?

Teenagers
Adults over 50
Young athletes

Many adults over 50 have too little stomach acid to absorb B12 from food.

Frequently Asked Questions

What are the first signs of low B12?

Tiredness, weakness, pale skin and tingling in hands or feet.

Can low B12 cause nerve damage?

Yes. It may become permanent if not treated promptly.

Do vegans need B12 supplements?

Usually. Fortified foods or a supplement are recommended.

Does metformin lower B12?

It can. Ask your doctor about regular testing.

Conclusion

Vitamin B12 deficiency is common in some groups and easy to miss. Tiredness, tingling and memory changes are reasons to get checked.

Eat B12-rich or fortified foods and talk with your doctor about testing if you are at risk.

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Editor’s Note

This guide is accurate as of November 10, 2026. It draws on the NIH Office of Dietary Supplements, MedlinePlus and Harvard T.H. Chan School of Public Health.

Ask your doctor about your own B12 needs.

Spot an error in this article? Please contact us at support@digieh.com or read our Corrections Policy.

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