Vitamin B12 Deficiency: Signs and Causes

Vitamin B12 is an essential nutrient that helps support red blood cells, a healthy nervous system, DNA production, and energy metabolism. Because the body does not make vitamin B12 on its own, you need to get it from fortified foods, nutritional shakes, or supplements.¹

Some people may be more likely to have lower B12 levels than others, including older adults, people who follow vegan or vegetarian diets, people with certain digestive conditions, and people who take certain medications. The good news: once low B12 is identified, a healthcare provider can help recommend the right next steps.

Key Takeaways:

• Vitamin B12 helps keep blood and nerve cells healthy and helps the body make DNA.
• B12 is found naturally in animal foods and can also be found in fortified foods and nutritional drinks.
• Signs of B12 deficiency can include fatigue, weakness, balance problems, tingling in the hands or feet, memory changes, and mood changes.

What is Vitamin B12?

Vitamin B12 is a water-soluble B vitamin that the body uses to help make DNA, support red blood cells, and maintain healthy nerve cells. It's naturally present in some foods, added to others, and available as a supplement.²

Vitamin B12 also plays a role in energy metabolism, which is the process your body uses to help turn food into energy.³

What Does Vitamin B12 Do?

Vitamin B12 helps support several important body functions:²

How Much B12 Do I Need?

Adults aged 50 and older should also pay attention to B12 intake because some people absorb less vitamin B12 from food as they age. Fortified foods, nutritional drinks, or supplements may be easier for some adults to absorb, but supplement needs should be discussed with a healthcare provider.

What Causes Vitamin B12 Deficiency?

Vitamin B12 deficiency can happen when someone does not get enough B12, does not absorb enough B12, or has higher needs due to life stage or health status. Common factors that may contribute to low B12 include:¹

• Older age
• Vegan or strict vegetarian diets
• Limited intake of animal foods or fortified foods
• Certain digestive conditions, such as Crohn’s disease or celiac disease
• A history of bariatric or stomach surgery
• Pernicious anemia, a condition that affects B12 absorption
• Long-term use of certain medications, including some medications for stomach acid or diabetes

What are Signs of a Vitamin B12 Deficiency?

B12 deficiency symptoms develop gradually and can be easy to confuse with other health concerns. That is why it is important to talk with a healthcare provider if symptoms persist.

Possible signs of B12 deficiency may include:^1,3

• Tiredness or fatigue
• Weakness
• Pale skin
• Shortness of breath
• Dizziness or lightheadedness
• Tingling or numbness in the hands or feet
• Balance problems
• Sore or smooth tongue
• Loss of appetite
• Memory changes
• Confusion
• Mood changes, such as feeling down or irritable

Foods Containing B12

Vitamin B12 is found naturally in animal foods. It can also be added to fortified foods and beverages.

Good sources of vitamin B12 include:^4,5

• Fish and seafood (clams, trout, salmon, and tuna)
• Meat and poultry (beef, liver, chicken, and turkey)
• Eggs
• Dairy foods (milk, yogurt, and cheese)
• Fortified cereals
• Nutritional yeast
• Fortified nutritional drinks

People who follow vegan diets should pay special attention to fortified foods or supplements, since plant foods do not naturally contain vitamin B12 in reliable amounts.

How to Help Support B12 Levels

You can help support vitamin B12 intake by:

• Eating a variety of foods containing B12
• Choosing appropriate fortified foods or nutritional drinks when they fit your routine
• Talking with your healthcare provider if you follow a vegan or vegetarian diet
• Asking about B12 testing if you have symptoms or risk factors
• Checking with your healthcare provider before starting a supplement, especially if you take prescription medications

Find BOOST® Products With Vitamin B12

Looking for a convenient way to support daily nutrition? BOOST® nutritional shakes include vitamins and minerals, including vitamin B12, and can help fill nutritional gaps as part of a balanced diet.

Explore BOOST® nutritional drinks to find an option that fits your needs, whether you are looking for everyday nutrition, high protein, or additional calories.

This article is for general informational purposes and is not a substitute for medical advice. Talk with your healthcare provider or registered dietitian about your individual B12 needs.

SOURCES:

1. Vitamin B12. National Institutes of Health. https://ods.od.nih.gov/factsheets/VitaminB12-Consumer. Accessed 6/17/2026.
2. Vitamin B12. National Institutes of Health. https://ods.od.nih.gov/factsheets/VitaminB12-HealthProfessional/. Accessed 6/17/2026.
3. Vitamin B12 in Health and Disease. Nutrients. https://www.mdpi.com/2072-6643/2/3/299. Accessed 9/23/2026.
4. The A list for vitamin B-12 sources. Harvard Health Publishing. https://www.health.harvard.edu/healthy-aging-and-longevity/the-a-list-for-vitamin-b-12-sources. Accessed 6/17/2026.
5. Top 12 Foods That Are High in Vitamin B12. HealthLine. https://www.healthline.com/nutrition/vitamin-b12-foods. Accessed 6/17/2026.