Vitamin B12 is essential for producing healthy red blood cells and maintaining nerve function, and because your body can only absorb it through a specific process involving stomach acid and a protein called intrinsic factor, deficiency is more common than many people realize, especially among older adults, vegans and vegetarians, and anyone with digestive conditions.
According to the National Institutes of Health Office of Dietary Supplements, B12 deficiency can develop slowly over years, since the body stores several years’ worth in the liver, which is part of why symptoms are often mistaken for other conditions until they’ve progressed. Left unaddressed, deficiency can eventually cause irreversible nerve damage, which is why catching it early matters.
Here are 12 signs that may point to low B12, who’s most at risk, and how to address it.
1. Persistent Fatigue and Weakness
Because B12 is essential for producing healthy red blood cells, deficiency can lead to a form of anemia that leaves the body short on oxygen-carrying capacity, resulting in fatigue that doesn’t improve with rest.
2. Pale or Slightly Yellow Skin
B12-deficiency anemia can cause red blood cells to break down more easily, releasing bilirubin and giving the skin a pale or subtly jaundiced appearance.
3. Pins and Needles Sensation
B12 is critical for maintaining the protective sheath around nerves, and deficiency can cause tingling or numbness, often starting in the hands and feet.
4. Difficulty Walking or Balance Issues
As nerve damage progresses, some people notice unsteadiness or difficulty with coordination, particularly in more advanced or prolonged deficiency.
5. A Sore, Red, or Swollen Tongue
Glossitis, a swollen and inflamed tongue that may also appear unusually smooth, is a classic and often early sign of B12 deficiency.
6. Mouth Ulcers
Recurring mouth ulcers have been associated with B12 deficiency, sometimes appearing alongside tongue changes.
7. Vision Disturbances
In more severe or prolonged cases, B12 deficiency can affect the optic nerve, leading to blurred or disturbed vision.
8. Mood Changes and Depression
B12 plays a role in neurotransmitter synthesis, and low levels have been linked to depression, irritability, and general low mood.
9. Memory Problems and Brain Fog
Because B12 supports nerve and cognitive function, deficiency can present as difficulty concentrating, forgetfulness, or a general mental fogginess, especially in older adults.
10. Rapid Heartbeat or Palpitations
As the body tries to compensate for reduced oxygen-carrying capacity from anemia, some people experience a faster or irregular heartbeat.
11. Unexplained Weight Loss
Reduced appetite alongside digestive symptoms sometimes associated with B12 deficiency can contribute to gradual, unintended weight loss.
12. Shortness of Breath
Like fatigue, breathlessness during normal activity can result from the reduced oxygen-carrying capacity that comes with B12-deficiency anemia.
Who’s Most at Risk
- Vegans and strict vegetarians: B12 occurs almost exclusively in animal products, making plant-based eaters reliant on fortified foods or supplements.
- Older adults: stomach acid production naturally declines with age, reducing the body’s ability to absorb B12 from food.
- People with digestive conditions: Crohn’s disease, celiac disease, and gastric bypass surgery can all interfere with B12 absorption.
- People taking certain medications: long-term use of metformin or acid-reducing medications like proton pump inhibitors can lower B12 absorption over time.
- People with pernicious anemia: an autoimmune condition that prevents the body from making the intrinsic factor needed to absorb B12.
Food Sources and Supplementation
B12 is found naturally in animal products: meat, poultry, fish, eggs, and dairy. Fortified foods like nutritional yeast, plant milks, and some breakfast cereals provide B12 for those eating plant-based. Because absorption can be a limiting factor regardless of intake, some people, particularly older adults or those with absorption issues, may need supplements or B12 injections even if their diet includes animal products.
When to See a Doctor
A blood test can measure B12 levels directly, and your doctor may also check for related markers like methylmalonic acid if levels are borderline. If you’re experiencing several of these symptoms, particularly the neurological signs like tingling or balance issues, it’s worth getting tested rather than waiting, since nerve damage from prolonged deficiency isn’t always fully reversible.
The Bottom Line
B12 deficiency develops slowly and its symptoms often overlap with other conditions, which is why it can go unnoticed for years. If several of these signs sound familiar, especially if you’re vegan, vegetarian, older, or have a digestive condition, a simple blood test can confirm whether low B12 is the cause and get you started on treatment before symptoms progress.
This article is for informational purposes only and is not a substitute for professional medical advice. Always talk to a doctor before starting B12 supplementation or making significant dietary changes.
