Vitamin B12 is a small but essential nutrient that plays a major role in your body. It helps keep your brain and nervous system healthy, supports red blood cell production, and is needed to make DNA.
When your B12 levels are too low, the symptoms can be easy to overlook. You might simply feel more tired than usual, have trouble concentrating, or notice tingling in your hands or feet.
The good news is that vitamin B12 deficiency is usually treatable. However, how quickly you feel better depends on how severe the deficiency is, what caused it, and how long you have had it.
What Is Vitamin B12?
Vitamin B12, also called cobalamin, is a water-soluble vitamin found naturally in foods such as:
Beef, poultry, and other meats
Fish and seafood
Eggs
Milk and other dairy products
Some breakfast cereals, plant-based milks, nutritional yeast, and other foods are also fortified with B12.
Your body needs B12 for several important functions, including maintaining healthy nerve cells, producing red blood cells, and making DNA.
What Causes Vitamin B12 Deficiency?
A B12 deficiency doesn’t always mean you’re simply not eating enough B12. Several different factors can cause it.
1. Not Getting Enough B12 From Your Diet
Because natural B12 is mainly found in animal foods, people who follow a vegan or strict vegetarian diet may be at greater risk if they don’t regularly consume fortified foods or take a B12 supplement.
2. Problems Absorbing B12
Your body may receive enough B12 from food but still have difficulty absorbing it.
Conditions affecting the stomach or intestines can interfere with B12 absorption. Certain surgeries, including some weight-loss surgeries, can also increase the risk.
An autoimmune condition called pernicious anemia can make it difficult for the body to absorb B12 properly.
3. Certain Medications
Long-term use of some medications may also be associated with lower B12 levels.
These include metformin, commonly used to manage type 2 diabetes, and certain medications that reduce stomach acid, such as proton pump inhibitors.
If you take these medications regularly, talk with your healthcare provider before making changes to your treatment.
13 Possible Signs of Vitamin B12 Deficiency
B12 deficiency can affect different parts of the body, and the symptoms aren’t always obvious.
Here are some signs worth knowing about.
1. Constant or Unusual Fatigue
Everyone gets tired sometimes. But B12 deficiency can cause persistent fatigue or weakness that doesn’t seem to improve with adequate sleep.
One reason is that severe B12 deficiency can lead to megaloblastic anemia, which affects the production of healthy red blood cells.
If you’re constantly exhausted without an obvious explanation, it’s worth talking with a healthcare professional.
2. Brain Fog and Trouble Concentrating
Do you find yourself forgetting words, losing your train of thought, or having trouble concentrating?
B12 deficiency can affect the nervous system and may contribute to cognitive changes.
However, brain fog has many possible causes, including poor sleep, stress, medications, thyroid problems, and other nutritional deficiencies. B12 testing can help determine whether a deficiency is involved.
3. Tingling or Numbness
One of the more important symptoms to watch for is pins-and-needles or numbness, particularly in the hands and feet.
B12 is essential for healthy nerve function. When levels remain low, nerve-related symptoms can develop.
Don’t ignore persistent or worsening numbness, especially if it is accompanied by weakness or balance problems.
4. Balance Problems or Unsteadiness
Some people with significant B12 deficiency develop problems with coordination or balance.
You may feel unsteady when walking or notice that you are stumbling more than usual.
Because balance problems can have many causes, they should be evaluated by a healthcare professional rather than automatically attributed to B12 deficiency.
5. Mood Changes
B12 deficiency can sometimes be associated with changes in mood, including depression.
This doesn’t mean that every mood change is caused by a vitamin deficiency. Mental health symptoms can have many different causes, so proper evaluation is important.
6. Pale Skin
If your skin suddenly looks noticeably paler than usual, anemia could be one possible explanation.
Severe B12 deficiency can interfere with normal red blood cell production and lead to anemia.
7. A Sore or Swollen Tongue
Changes inside your mouth can sometimes occur with B12 deficiency.
You may notice a sore, swollen, smooth, or unusually red tongue. Some people may also experience mouth discomfort.
8. Heart Palpitations or Shortness of Breath
When B12 deficiency causes anemia, your body may have difficulty delivering enough oxygen to tissues.
As a result, you may experience symptoms such as:
Shortness of breath, particularly with activity
A faster heartbeat
Heart palpitations
Weakness or fatigue
These symptoms can have many causes. If you experience new or significant shortness of breath or heart palpitations, seek medical advice rather than assuming it’s a vitamin deficiency.
9. Reduced Appetite or Unintentional Weight Loss
Some people with B12 deficiency may experience a reduced appetite or unexplained weight loss.
If you’re losing weight without trying, it’s important to speak with a healthcare professional because there are many possible underlying causes.
10. Headaches
Headaches can occur alongside B12 deficiency, particularly when anemia is present.
However, headaches are extremely common and are usually caused by many other factors. A headache by itself isn’t a reliable sign of B12 deficiency.
11. Muscle Weakness
Low B12 levels can affect the nervous system and may contribute to muscle weakness.
If weakness is persistent, getting worse, or affecting your ability to walk or perform everyday activities, medical evaluation is important.
12. Vision Changes
In rare cases, severe or prolonged B12 deficiency can affect the optic nerve and cause vision problems.
New blurred vision or other sudden changes in eyesight should always be evaluated promptly rather than assumed to be caused by B12.
13. Memory or Thinking Problems
Some people with B12 deficiency develop problems with memory, concentration, or thinking.
Because these symptoms can also occur with aging, stress, sleep disorders, medications, and other medical conditions, testing may be necessary to identify the underlying cause.
Who Is Most at Risk for Vitamin B12 Deficiency?
Certain groups are more likely to develop low B12 levels, including:
Adults over age 50
People following a vegan or strict vegetarian diet
People with gastrointestinal disorders that affect nutrient absorption
People who have undergone certain stomach or intestinal surgeries
People with pernicious anemia
People taking metformin for long periods
People taking certain acid-reducing medications
If you fall into one of these groups, ask your healthcare provider whether B12 testing is appropriate for you.
How Much Vitamin B12 Do You Need?
The recommended daily amount for most adults in the United States is 2.4 micrograms (mcg) of vitamin B12 per day.
The recommended amount is slightly higher during pregnancy and breastfeeding:
Adults: 2.4 mcg per day
Pregnancy: 2.6 mcg per day
Breastfeeding: 2.8 mcg per day
These amounts are intended to meet normal nutritional needs. They are not treatment doses for someone who has been diagnosed with a B12 deficiency.
If you have a confirmed deficiency, your healthcare provider may recommend a much higher dose depending on the cause and severity of the deficiency.
How Is Vitamin B12 Deficiency Diagnosed?
Symptoms alone aren’t enough to diagnose a B12 deficiency because many of them overlap with other health conditions.
A healthcare provider may order a blood test to check your B12 level. Depending on the results and your symptoms, additional tests may be needed.
In some cases, doctors use a test called methylmalonic acid (MMA) to help determine whether a person’s B12 status is inadequate.
The important thing is to identify why the B12 level is low, not just increase the vitamin temporarily.
How Long Does It Take to Recover From B12 Deficiency?
Recovery time varies considerably from person to person.
Some symptoms may begin improving relatively quickly after appropriate treatment, while neurological symptoms such as numbness, tingling, and balance problems can take much longer.
If the deficiency has been severe or untreated for a long time, some nerve damage may not completely reverse.
That’s why early diagnosis and treatment are especially important when neurological symptoms are present.
Can You Prevent Vitamin B12 Deficiency?
For many people, getting enough B12 is straightforward.
Regularly eating B12-rich foods or consuming fortified foods can help meet your nutritional needs. People who don’t consume animal products may need fortified foods or a B12 supplement.
If you have a medical condition that affects B12 absorption, however, simply changing your diet may not be enough. You may need supplementation or medical treatment recommended by your healthcare provider.
The Bottom Line
Vitamin B12 deficiency can be easy to miss because its symptoms can develop gradually.
Unexplained fatigue, numbness or tingling, balance problems, weakness, pale skin, changes in mood, and difficulty concentrating can all occur with B12 deficiency, particularly when the deficiency is significant.
But these symptoms don’t automatically mean you are deficient. The same problems can occur for many other reasons.
If you think you may have low B12—especially if you’re over 50, follow a vegan diet, take metformin or acid-reducing medication, or have a condition affecting nutrient absorption—talk with a healthcare professional about whether testing is appropriate.
The earlier a true B12 deficiency is identified and treated, the better the chance of preventing long-term complications.
