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Vitamin B-12 deficiency symptoms: What are the early signs of B-12 deficiency?

Medically reviewed by Stephanie Melby, Pharm.D.
Licensed Pharmacist
Updated Oct. 27, 2023  •  Published Mar. 1, 2023
Fact Checked
Vitamin B-12 deficiency symptoms

Overview: What does B-12 deficiency feel like?

Vitamin B-12 is essential to the body’s ability to use DNA to make new cells, keep nerves healthy, and synthesize fats. If there’s insufficient vitamin B-12 in the body, then nearly every part of the body is affected. Because B-12 is needed to make cells, fast-growing tissues, especially blood cells, are the first to be affected. If there’s not enough vitamin B-12, the body can’t make enough blood cells, and the ones that are made are too big, a condition called megaloblastic anemia. For this reason, nearly everyone with a long-lasting vitamin B-12 deficiency will eventually feel tired, worn out, and their skin will be pale and clammy because they don’t have enough blood cells. Nerves are also affected, so people will notice their body isn’t working right. Balance is off, coordination doesn’t work well, and hands and feet may feel numb or painful. Eventually in severe cases, the brain is affected. People start forgetting things, getting irritated, depressed, confused, and sometimes psychotic. Fortunately, a B-12 deficiency can be quickly reversed by taking high-dose B-12 supplements or getting high-dose B-12 injections.

RELATED: 9 common nutrient deficiencies in the U.S.

Key takeaways:

  • B-12 deficiency is a common health condition that mostly affects older adults.

  • Early signs of B-12 deficiency include fatigue, pale skin, tongue swelling, and possibly jaundice.

  • Serious symptoms of B-12 deficiency, such as delirium or dementia, may require immediate medical attention.

  • B-12 deficiency is caused by diet, an autoimmune response, stomach or intestinal surgery, digestive system disorders, or some drugs. You may be at risk for developing B-12 deficiency symptoms if you are elderly; of European descent; malnourished; have had stomach surgery, gastric bypass, or removal of part of the bowel; have medical conditions such as Crohn’s disease, atrophic gastritis, celiac disease, or a tapeworm; are taking certain medications including heartburn or ulcer drugs; or follow a vegan diet or a strict vegetarian diet.

  • B-12 deficiency requires a medical diagnosis.

  • Symptoms of B-12 deficiency generally do require treatment. They typically resolve with treatment in one to 12 weeks depending on the symptoms.

  • Treatment of B-12 deficiency may include B-12 supplements or regular injections of vitamin B-12.

  • Untreated B-12 deficiency could result in complications like anemia, disabling nerve or central nervous system damage, or heart failure. A B-12 deficiency also raises the risk of stomach cancer and certain autoimmune disorders.

  • Use coupons for a vitamin B-12 prescription to save up to 80%.

What are the early signs of B-12 deficiency?

The early signs of B-12 deficiency are usually related to anemia and include:

  • Fatigue

  • Pale skin

Other early signs might include:

Other B-12 deficiency symptoms

Anemia symptoms are the primary signs of a vitamin B-12 deficiency. These include:

  • Fatigue

  • Pale skin

  • Yellowing of the skin

Other symptoms include:

  • Red patches on the tongue

  • Swollen tongue

  • Lesions on the tongue or inside of the mouth

  • Headache

  • Diarrhea

More serious symptoms are related to nerve damage. These include:

  • Numbness or tingling in the fingers, toes, hands, or feet

  • Soreness or burning in the mouth

  • Slow reflexes

  • Abnormalities in walking

  • Loss of balance

  • Loss of coordination

  • Eye problems

  • Irritability

  • Depression

  • Memory problems

  • Confusion

  • Disorientation

  • Psychosis

  • Dementia

RELATED: Common vitamin deficiencies in the U.S.

B-12 deficiency vs. folate deficiency symptoms

The body needs both vitamin B-12 and vitamin B9 (folate) to make healthy red blood cells. B-12 is important because it is a factor in producing enzymes needed to make new red and white blood cells. B9 is important in several processes involved in making red blood cells. If one of these is too low, the body can’t make enough red blood cells and hemoglobin to provide needed oxygen to the rest of the body. The symptoms will be similar. Like vitamin B-12, vitamin B9 is also important to healthy nerve functioning. For both vitamin B deficiencies, many of the neurological symptoms are the same, as well.

B-12 deficiency Folate deficiency
Shared symptoms
  • Fatigue
  • Pale or clammy skin
  • Beefy red tongue
  • Mouth sores
  • Diarrhea
  • Headache
  • Shortness of breath
  • Muscle weakness
  • Loss of taste
  • Peripheral neuropathy symptoms such as tingling, numbness, or weird sensations in the hands, fingers, toes, and feet
  • Cognitive impairment including memory problems, memory loss, concentration problems, confusion, and dementia
  • Psychiatric symptoms such as depression and irritability
Unique symptoms
  • Jaundice
  • Symptoms typically develop over the course of years
  • Symptoms can develop rapidly (weeks to months)

RELATED: Why pregnant women need to take folic acid

Stages of B-12 deficiency: How can I tell which one I have? 

Some articles or sites may talk about “stages of B-12 deficiency.” However, doctors and other healthcare providers don’t use “stages” to diagnose or treat B-12 deficiency. Here’s why. Some healthcare professionals previously distinguished between four stages of B-12 deficiency. In the first two stages, people don’t get enough B-12, but there are no symptoms. A doctor needs to measure B-12 in the blood. Fortunately, the liver stores almost 10 years’ worth of vitamin B-12, so a B-12 deficiency can go on for a while without health problems. In the third stage, a vitamin B-12 deficiency can be detected by doing lab tests that show that the body’s chemistry is not working right. In the last stage, B-12 deficiency causes symptoms, particularly symptoms of anemia. Since healthcare professionals only routinely screen people for B-12 deficiency if they have certain risk factors, the diagnosis is usually made after symptoms appear.

When to see a doctor for B-12 deficiency symptoms

If any of the symptoms of a vitamin B-12 deficiency are noticed, see a doctor. The same applies to any symptoms of anemia, nerve damage, or central nervous system problems no matter what the cause. The consequences of leaving these untreated can be severe.

A healthcare provider will diagnose B-12 deficiency by taking a medical history, performing a physical examination, and taking blood tests. The medical history is important for figuring out the cause of the deficiency. Be prepared to tell the medical professional about diet, drinking, surgeries, gastrointestinal maladies, or any drugs that are regularly taken, especially metformin or heartburn drugs like proton pump inhibitors or H2 blockers. A physical exam will look for neurological problems, swollen tongue, and skin changes. 

However, the diagnosis is confirmed by blood tests. These can show vitamin B-12 levels in the blood, a complete blood count, and the amount of hemoglobin in the blood (MCH test). If there are low levels of vitamin B-12, that’s enough to make a diagnosis and start vitamin B-12 supplements. However, some people with a B-12 deficiency don’t have a low enough serum B-12 to get a diagnosis. Other blood tests may be needed to make sure.

RELATED: What are normal MCH levels?

Complications of B-12 deficiency

If there is a B-12 deficiency, B-12 must be brought back to normal to prevent complications, which include:

  • Anemia

  • Nerve damage

  • Degeneration of the spinal cord

  • Debilitating neurological deficits

  • Heart failure

  • Increased risk of stomach cancer

  • Increased risk of autoimmune diseases including rheumatoid arthritis and myasthenia gravis

How to treat B-12 deficiency symptoms

Treatment is simple: vitamin B-12 levels in the blood need to be brought back to normal levels. This is usually accomplished by prescribing high-dose vitamin B-12 supplements. In severe cases, intramuscular high-dose injections may be required. Treatment typically lasts for a few weeks or a few months. However, if there’s a cause that needs treatment, then supplementation will continue until the cause is successfully treated. Note: Taking vitamin C at the same time as vitamin B-12 could result in malabsorption and reduce the amount of B-12 that’s metabolized by the body. Try to space the two vitamins out by two or more hours. If the cause is irreversible , like pernicious anemia or those who have had bariatric surgery, then B-12 supplements or injections will probably continue throughout a person’s life.

RELATED: How to make sure you absorb your supplements

Signs B-12 deficiency is getting better

For people without symptoms, their blood tests should return to normal after about a week of treatment. Anemia usually resolves within two months after the start of B-12 supplementation. Neurological problems can take as long as three months to get better. Some neurological deficits may be permanent. 

To prevent B-12 deficiency, make sure to consume enough B-12 in the diet. The recommended daily allowance for adults is 2.4 micrograms per day, slightly higher for women who are pregnant or breastfeeding. The best foods for getting enough vitamin B-12 are dairy products, animal products, nutritional yeast, and cereals fortified with vitamin B-12. Otherwise, a daily cobalamin dietary supplement or multivitamin should be enough.

Most importantly, B-12 deficiency can be quickly resolved if you see a doctor

If you experience symptoms typical of a B-12 deficiency, see a healthcare professional for medical advice. It’s not an emergency, but it’s also not something that should be left for later. A B-12 deficiency can be easily reversed with B-12 supplements or injections. Do not try to self-diagnose and self-treat the symptoms. The symptoms may be due to other causes. Only a doctor or other healthcare professional can accurately diagnose the cause of the symptoms and start appropriate treatment.

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FAQs about B-12 deficiency symptoms

What are the neurological symptoms of a B-12 deficiency?

A severe or chronic B-12 deficiency can damage the body’s nerves, particularly those in the central nervous system. Initial symptoms are usually tingling, numbness, or weird sensations in the extremities like fingers and toes. As the nerve damage in the central nervous system worsens, people begin to experience balance problems and find it hard to coordinate their movements. Irritability, depression, memory problems, dementia, confusion, and disorientation are some of the most serious and debilitating neurological effects of B-12 deficiency.

Why does a B-12 deficiency cause neurological problems?

Vitamin B-12 is an important factor in producing certain enzymes in the body. If it’s too low, then chemicals that normally develop into those enzymes build up in the body. Two of those chemicals (MMA and homocysteine) damage the protective sheath that surrounds many nerves in the central nervous system. 

What does a B-12 deficiency tongue look like?

Some of the earliest symptoms of a B-12 deficiency are “beefy red” patches on the tongue. As the B-12 deficiency persists, eventually the entire tongue can swell up with bright red areas that look like sores. These bright red sores can also appear on the palate, inner cheeks, or lips.  

What are pernicious anemia symptoms?

The most common symptoms of pernicious anemia are fatigue, pale skin, and a red, beefy tongue. If these symptoms sound familiar, it’s because pernicious anemia is a type of vitamin B-12 deficiency. However, for pernicious anemia, the cause of the B-12 deficiency is an autoimmune reaction that compromises the stomach’s ability to make intrinsic factor, a chemical that the body needs to absorb vitamin B-12.

What’s next? Additional resources for people with B-12 deficiency symptoms

Test and diagnostics

Treatments

Scientific studies and clinical trials

Medically reviewed by Stephanie Melby, Pharm.D.
Licensed Pharmacist

Stephanie Melby, B.S., Pharm.D., received a bachelor of science in nutrition from the University of Minnesota and a doctorate of pharmacy from the University of New England. She has seven years of experience in retail pharmacy and is certified in Medication Therapy Management (MTM). Dr. Melby resides in Minneapolis, Minnesota.

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