Vitamin B12 deficiency can affect your body in many different ways. This essential vitamin plays a key role in nerve function, red blood cell production, and DNA creation.

The condition shows up differently in each person.

Signs and Symptoms of Vitamin B12 Deficiency

Here are 16 signs and symptoms that can help you recognize vitamin B12 deficiency early. These symptoms can appear alone or in combination, and their severity varies from person to person.

1. Fatigue and Weakness

If you’re deficient in B12, you’ll likely feel fatigued. Your body’s cells need B12 to function properly.

A 2024 study found fatigue was the most common complaint in 66.7% of patients with deficiency (1). This happens because your body needs B12 to make healthy red blood cells that carry oxygen to your tissues.

2. Pale or Yellowish Skin

Your skin may look paler than usual when you have vitamin B12 deficiency. Some people also develop a slight yellow tint to their skin and eyes.

A 2017 case report documented a patient with B12 deficiency who presented with both pallor and jaundice (2). This occurs due to a buildup of bilirubin, a waste product from breaking down red blood cells. The deficiency causes your red blood cells to break down faster than normal.

3. Tingling and Numbness

Tingling and numbness are among the most common nerve symptoms of vitamin B12 deficiency. Research from 2024 documents that these sensations in the hands and feet affected 54.4% of patients (1). These sensations usually start in your feet and hands.

This symptom develops because vitamin B12 is essential for producing myelin. Myelin is the protective coating around your nerves (3).

Warning
Nerve damage from vitamin B12 deficiency can become permanent if left untreated. Early diagnosis and treatment are crucial to prevent long-term problems.

4. Loss of Balance and Coordination

Loss of coordination is a common early sign of vitamin B12 deficiency. Studies show that ataxia, or loss of coordination, is a characteristic feature (4). You may feel unsteady when walking or have trouble with precise movements.

Nearly all patients show loss of vibratory sensation and problems with position sense (5).

5. Memory Problems and Confusion

Vitamin B12 deficiency can affect your brain function. Cognitive symptoms can range from mild memory problems to severe confusion.

Research found dementia can develop as a result of vitamin B12 deficiency (4). These cognitive changes happen because vitamin B12 is vital for brain health and helps maintain the protective covering around nerve cells in your brain.

6. Depression and Mood Changes

Low vitamin B12 levels can have a significant impact on your mental health. People with vitamin B12 deficiency are twice as likely to have severe depression (6). This connection exists even when other health problems are taken into account.

A 2023 study also found that lower vitamin B12 levels were linked to more severe anxiety symptoms (7).

7. Glossitis and Mouth Sores

Glossitis means tongue inflammation. Your tongue may appear smooth, swollen, and red when you have a vitamin B12 deficiency.

A 2017 study found vitamin B12 deficiency in patients with tongue changes (8). The small bumps on your tongue can disappear completely, making it look smooth and shiny.

Some people also develop mouth sores. These can be painful and make eating uncomfortable.

8. Vision Problems

Blurry or disturbed vision can occur with vitamin B12 deficiency. Studies show that optic neuropathy, or nerve damage to the eye, is a serious manifestation of vitamin B12 deficiency (9).

This happens when the deficiency damages the optic nerve, which carries signals from your eye to your brain. If you notice unexplained vision problems, you should see a doctor right away.

9. Shortness of Breath and Dizziness

You may feel short of breath or dizzy when you have a vitamin B12 deficiency. Research documents that shortness of breath on exertion is a symptom of severe B12 deficiency-related anemia (10).

These symptoms develop because your body cannot produce enough healthy red blood cells to carry oxygen. Your heart has to work harder to pump oxygen throughout your body.

You may also notice cold hands and feet as a related symptom. Research shows cold extremities can occur with vitamin B12 deficiency (11). This happens because reduced red blood cells mean less oxygen reaches your extremities, affecting circulation and causing a cold sensation.

10. Muscle Weakness

Vitamin B12 deficiency can reduce muscle strength and quality. A 2024 study found that vitamin B12 deficiency contributes to reduced muscle strength and physical performance among older people (12). This weakness can affect your ability to perform daily tasks.

Evidence shows muscle weakness becomes more noticeable as the deficiency gets worse (13). In older adults, vitamin B12 deficiency can lead to more serious problems like sarcopenia and frailty. Sarcopenia refers to the loss of muscle mass and function that happens with aging. Research shows vitamin B12 deficiency plays a role in these conditions (14).

Frailty is characterized by reduced functional abilities and increased vulnerability. Studies indicate that vitamin B12 deficiency contributes to frailty by affecting physical and cognitive function (14). This can make you more dependent on others for daily activities and increase your risk of falls and other health problems.

11. Headaches

Headaches are among the most commonly reported symptoms of vitamin B12 deficiency. Multiple studies have found that vitamin B12 levels in people with migraines are much lower than in healthy people (15, 16). People with chronic migraines have even lower levels. In one study, those with the poorest B12 function were more than five times more likely to have migraines.

12. Gastrointestinal Problems

Vitamin B12 deficiency can cause a wide range of gastrointestinal issues. Research shows vitamin B12 deficiency contributes to various gastrointestinal disorders (17, 18).

A 2009 study found that patients with low vitamin B12 levels had a higher rate of gastrointestinal diseases (19). Common problems include nausea, constipation, diarrhea, bloating, and gas.

A 2018 systematic review confirms that gastrointestinal disorders are closely linked to vitamin B12 deficiency (20). These symptoms can affect both adults and children.

13. Erectile Dysfunction

Low vitamin B12 levels can affect sexual function in men. Multiple studies have found that men with erectile dysfunction have lower vitamin B12 levels than healthy men (21, 22). The deficiency is more pronounced in younger men.

Note
Many symptoms of vitamin B12 deficiency can overlap with other health conditions. This makes it important to get proper testing rather than self-diagnosing based on symptoms alone.

14. Developmental Delays in Infants

Vitamin B12 deficiency can seriously affect babies and young children. A large 2023 review that looked at 292 infants found that symptoms usually start to show up when babies are around four months old (23).

Children may show developmental delays, even without obvious symptoms. A 2023 study found that children with B12 deficiency had significantly higher rates of abnormal neurodevelopmental screening results (24).

15. Difficulty Concentrating

You may feel foggy-headed and have trouble focusing on tasks. Vitamin B12 is essential for your nervous system to work properly, and when levels are low, your brain cannot function at its best.

Research documents concentration difficulty as a symptom in both children and adults (25).

16. Rapid Heartbeat and Heart Rhythm Problems

Vitamin B12 deficiency can affect your heart rhythm and cardiovascular function. A 2022 study of 214 healthy adults found that people with low vitamin B12 levels had cardiac autonomic dysfunction, problems with heart rate variability, and significant heart rhythm abnormalities on their electrocardiograms (26). These changes indicate an increased risk for dangerous heart rhythm problems.

Vitamin B12 deficiency has also been linked to a condition called postural orthostatic tachycardia syndrome, or POTS. This condition causes your heart to beat very fast when you stand up. A 2014 study found that adolescents with POTS had much lower vitamin B12 levels than healthy controls (27). The deficiency may interfere with how your nervous system controls your heart rate and blood pressure.

Frequently Asked Questions

What is usually the first symptom of vitamin B12 deficiency?

The first symptom varies by person, but fatigue and weakness are often the earliest signs people notice. Tingling or numbness in the hands and feet is another common early warning sign, particularly in the lower limbs.

Can vitamin B12 deficiency cause weight loss?

Yes, weight loss can occur with vitamin B12 deficiency. This happens due to decreased appetite and digestive problems. Some people also experience unintentional weight loss as the deficiency affects their metabolism and overall health.

How long does it take for vitamin B12 deficiency symptoms to show?

The timeline varies greatly between individuals. Some people develop symptoms within months, while others may take years because the body stores vitamin B12 in the liver. Infants and children typically show symptoms faster than adults due to smaller vitamin stores.

How Long Before Vitamin B12 Deficiency Symptoms Become Serious?

The severity of your symptoms before treatment predicts long-term problems. Research shows that how severe your symptoms are before treatment correlates with lasting damage (5). The longer symptoms last without treatment, the worse the outcome. Studies warn that delays in treatment can lead to permanent nerve damage (28).

Can vitamin B12 deficiency cause permanent damage?

Yes, if left untreated, vitamin B12 deficiency can cause permanent nerve damage. The risk of permanent damage increases the longer the deficiency goes untreated. Early diagnosis and treatment are essential to prevent lasting problems.

Do you need to have low blood counts to have a vitamin B12 deficiency?

No, you can have a vitamin B12 deficiency without low blood counts. Studies found that up to 28% of patients with nerve symptoms from vitamin B12 deficiency had normal blood counts (4). The nervous system problems appeared before any blood changes. Studies emphasize that symptoms can occur without low blood counts, especially nerve symptoms (25). This makes diagnosis challenging.

What are the mental symptoms of vitamin B12 deficiency?

Mental symptoms include depression, anxiety, confusion, memory problems, and mood changes. These symptoms can occur without other signs of deficiency and may be the first warning signs in some people.

Can vitamin B12 deficiency cause sleep problems?

Yes, vitamin B12 deficiency has been linked to insomnia and sleep disturbances. Studies show that people with low B12 levels report more sleep problems than those with normal levels.

The Bottom Line

Vitamin B12 deficiency causes many different symptoms that affect your blood, nerves, mind, and overall health. Early warning signs include fatigue, tingling, pale skin, and mood changes.

These symptoms can appear long before blood problems develop. The key is recognizing them early and seeking proper testing. Treatment works best when started early, before permanent nerve damage occurs.

If you have symptoms that concern you, talk to your doctor about testing your vitamin B12 levels.

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