• Alyssa Fontaine, RD
• Nov 24, 2025

Does High Vitamin B12 Mean Cancer?

Vitamin B12 and Cancer

Perhaps you’ve heard that high vitamin B12 is “cancerous.” This kind of statement can sound scary and cause unnecessary fear. You might even think, “Maybe I should take less B12, just in case.” That’s a normal reaction, especially when no further explanation is given.

However, statements like this are often taken out of context. By the end of this article, you’ll understand where this idea came from and the true reality of vitamin B12.

What is B12?

Vitamin B12, also known as cobalamin, is an essential nutrient that our bodies cannot produce on their own. We need it to stay healthy, and here are just a few of its important roles:

• Helps make red blood cells stronger to avoid weakness and fatigue
• Protects the nerves and supports brain development
• Has a role in DNA production, especially in tissues that grow fast (organs, skin, hair, and nails)
• Keeps the digestive system healthly by maintaining the mucous lining of the gut
• Is a teamplayer to convert food into energy

Vitamin B12 is naturally found in animal-based foods, fortified products, and supplements. Fortified foods can be meat substitutes, plant based dairy products (milk and yogurt) and some brands of nutritional yeast. But do check the nutrition facts table to see if vitamin B12 is indeed added. 

If you are vegan or vegetarian and you want to know more about where to find vitamin B12 sources for you, click here. Or if you are curious for more information on B12 and children, we have this article available for you. 

How does B12 work in our bodies?

When you eat foods that contain vitamin B12, it is usually bound to proteins. With the help of saliva and stomach acid, B12 is released. It then binds to a special protein called intrinsic factor, which is produced in the stomach.

This B12 and intrinsic factor travels to the small intestine, where B12 is absorbed. At that point, intrinsic factor is released, and B12 binds to another protein to be transported through the bloodstream. From there, it can be delivered to the:

• Bone marrow for red blood cell development
• Nerves to make protection for them 
• Liver for storage 

High Blood B12 and Cancer

Eating foods high in B12 will not cause cancer. Let’s make that clear. Vitamin B12 is essential for normal body function. So, why does B12 sometimes get linked to cancer?

It was found people with liver cancer have unusually high B12 levels in their blood. This happens because the liver normally stores B12. When the liver is damaged by cancer or other disorders, it can release B12 into the bloodstream, making blood levels appear abnormally high. 

After a number of scientific studies, it was concluded that high blood B12 can be a marker of illness, but B12 itself does not cause cancer.

Curious for more?

If you’re unsure whether you’re not getting enough or too much B12, speak with your doctor or dietitian. If you’d like personalized counseling on vitamin B12 in your diet and supplements, click here for an appointment with us.

Bottom Line

Don’t worry, vitamin B12 is an essential nutrient that supports many vital functions in the body. Remember to think critically when you hear statements that sound overly simple or alarming. Most of the time, there’s more to the story than meets the eye.