What are the first signs of B12 deficiency?

Tiredness, weakness and pale skin are often the first signs. Tingling in the hands or feet and a sore tongue can follow, sometimes before anemia shows on a blood test.

What blood test checks for B12 deficiency?

A serum vitamin B12 level is the first test, usually with a complete blood count. If the result is borderline, a methylmalonic acid (MMA) test can help confirm it.

Does metformin cause B12 deficiency?

Long-term metformin can lower B12 levels. The FDA label advises checking B12 every two to three years and blood counts each year, and you should not stop metformin without talking to your doctor.

Can low B12 cause numbness and tingling?

Yes. Low B12 can damage nerves and cause numbness, tingling or a pins-and-needles feeling, often starting in the feet. These symptoms should be checked soon, because long-standing nerve damage may not fully reverse.

Can B12 deficiency cause hair loss?

Hair loss is not a main sign of B12 deficiency. Iron, thyroid and vitamin D problems are more common causes, and a doctor may check B12 along with them.

Are B12 pills or injections better?

It depends on the cause. High-dose pills work for many people, while injections are standard treatment for some causes such as pernicious anemia or some stomach and bowel surgeries.

How long does it take to recover from B12 deficiency?

Energy and blood counts often improve within weeks of treatment. Nerve symptoms can take months to improve and may not fully go away if they were present for a long time.

B12 Deficiency Symptoms and Tests

The most common B12 deficiency symptoms are tiredness and weakness, anemia, numbness or tingling in the hands and feet, a sore red tongue, and memory or mood changes. It is more likely after age 50, on a vegan diet, with long-term metformin or acid-reducing medicine, after stomach surgery, and with pernicious anemia. A blood test confirms it, and treatment with diet, B12 pills or B12 injections depends on the cause.

What is vitamin B12 and why does it matter?

Vitamin B12 helps your body make healthy red blood cells, keeps your nerves working, and is needed to make DNA. Your body cannot make it, so it has to come from food or supplements. It is found naturally in meat, fish, poultry, eggs and dairy, and is added to some cereals and nutritional yeast.

To absorb B12, your stomach needs acid to free it from food and a protein called intrinsic factor to carry it into the body. A problem at any step, from diet to stomach to gut, can lead to low levels. Because the body stores B12 in the liver, a deficiency often builds slowly over months or years.

What are the signs of B12 deficiency?

Early on there may be no symptoms. As levels fall, the most common signs are:

Tiredness, weakness and low energy
Pale skin, shortness of breath or a fast heartbeat from anemia
Numbness, tingling or a pins-and-needles feeling in the hands and feet
Trouble with balance or walking
A sore, swollen, smooth or red tongue, or mouth sores
Loss of appetite, weight loss or constipation
Memory problems, confusion, low mood or irritability

What does B12 deficiency do to the tongue?

A sore, red, smooth-looking tongue is a classic sign. The small bumps on the surface flatten out, and the tongue may feel tender or burn, especially with hot or spicy food. This is called glossitis. Low iron and low folate can cause it too, so a blood test sorts out which one it is.

What are the neurological symptoms of low B12?

B12 protects the nerves, so a deficiency can cause numbness and tingling, often starting in the feet, unsteady walking, and changes in memory, thinking or mood. These nerve symptoms can happen even when there is no anemia on a blood count. Nerve damage may become permanent if the deficiency is left untreated for a long time, which is why new numbness or balance problems should be checked soon.

Does B12 deficiency cause hair loss?

Hair loss is not one of the main signs of B12 deficiency. When someone has thinning hair and low energy, doctors usually also check iron, thyroid and vitamin D, since those are more common causes. A B12 test may be part of that workup.

Who is at risk for low B12?

You are more likely to have low B12 if you:

Are 50 or older, because many older adults make less stomach acid and absorb less B12 from food
Eat a vegan diet, or a vegetarian diet with few eggs and dairy
Take metformin for diabetes, prediabetes or PCOS
Take acid-reducing medicines for a long time, such as omeprazole, pantoprazole or famotidine
Have had weight loss surgery or surgery that removed part of the stomach or small intestine
Have Crohn's disease, celiac disease or another condition that affects the gut
Have pernicious anemia, an autoimmune condition in which the body cannot make intrinsic factor
Are pregnant or breastfeeding and follow a vegan diet, since babies can develop low B12 too

Metformin and B12: what should you know?

Metformin is a common, effective diabetes medicine, and long-term use can lower B12 levels. The FDA label for metformin notes this and advises checking blood counts each year and B12 levels every two to three years, or sooner if symptoms appear.

This matters because numbness and tingling from low B12 can look like nerve damage from diabetes. If you take metformin and notice new tingling in your feet, ask your doctor to check your B12. Do not stop metformin on your own. A low B12 level can usually be treated while you keep taking it.

How is B12 deficiency diagnosed?

A blood test is the only way to know. The usual tests are:

Serum vitamin B12 level: the first test for most people
Complete blood count (CBC): looks for anemia and for red blood cells that are larger than normal, a common pattern with low B12
Methylmalonic acid (MMA): this level rises when the body is short of B12, so it helps when the B12 result is borderline
Homocysteine: may also be high with low B12 or low folate
Intrinsic factor antibodies: checked when pernicious anemia is suspected

Lab ranges differ between labs, and a result in the low-normal range does not always rule out a problem. That is why MMA is sometimes added. Folate is often checked at the same time, because taking folic acid can hide the anemia of low B12 while the nerve damage keeps going.

How is B12 deficiency treated?

Treatment depends on the cause and how low your level is:

Food: for mild low levels from diet, more B12-rich foods or fortified foods may be enough. Adults over 50 are advised to get much of their B12 from fortified foods or supplements, since these are easier to absorb.
Pills: oral B12 supplements are widely used. High-dose pills can work for many people, even some with absorption problems.
Injections: B12 shots into the muscle are a standard medical treatment for some causes, such as pernicious anemia and some cases after stomach or bowel surgery. People with these conditions often need treatment for life.

After treatment starts, follow-up blood tests show whether levels and blood counts are improving. Tiredness and anemia often improve first. Nerve symptoms may take longer and may not fully go away if they have been present for a long time.

When should you see a doctor about B12?

Book a visit if you have any of the symptoms above, especially with a risk factor such as age over 50, a vegan diet, metformin or acid-reducing medicine. See a doctor soon for new numbness, tingling, balance trouble or memory changes. Go to the emergency room for sudden weakness, trouble speaking, chest pain or severe shortness of breath, since those need urgent care whatever the cause.

How Dr. Munib approaches low B12

Dr. Munib asks about your diet, medicines, stomach or bowel history, and symptoms such as tingling, balance or memory changes. The exam may include checking your tongue, skin color, reflexes and the feeling in your feet.

Labs usually include a B12 level and a CBC. Depending on the results, she may add MMA, folate, iron studies or a thyroid test, and look for the cause, such as pernicious anemia or medicine effects. Treatment options she may discuss include diet changes, oral B12 or B12 injections, depending on the cause and your results.

Read about preventive care and lab checkups at The Pur Health

Separately, The Pur Health lists a B12 and B-complex shot as an optional wellness service

If you think your B12 might be low, a simple blood test is the place to start. The Pur Health is in-network with most PPO plans, and cash visits are $190 for new patients and $150 for returning patients. Book a visit at our Irvine office at 114 Pacifica, Suite 280, or call (949) 647-5234.

B12 Deficiency Symptoms: Signs, Causes, Tests and Treatment