If you’ve been feeling unusually exhausted, foggy, or dealing with tingling in your hands and feet, you may have gone down a late-night Google spiral and landed on vitamin B12 deficiency.
And somewhere along the way, you probably saw the word cancer, which is enough to make anyone’s chest tighten.
So let’s talk straight. Can vitamin B12 deficiency be a sign of cancer? In rare cases, yes. But for most people, the cause is far more common and far less scary.
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Still, B12 deficiency isn’t something to ignore, especially if symptoms persist.
Understanding what’s behind it can help you get answers, relief, and peace of mind.
Why is Vitamin B12 Important?
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Vitamin B12 handles a lot of the everyday work your body depends on. It keeps nerves working, your red blood cells carrying oxygen, and your DNA replicating the way it should. When your levels drop, your whole system can feel it, from your energy to your memory to how well you move and think.
And yes, in some cases, low B12 can show up alongside certain cancers.
That doesn’t mean B12 deficiency causes cancer or even that it’s a solid sign of it. But some cancers, especially in the stomach or intestines, can interfere with how you absorb nutrients like B12.
Let’s get into what the symptoms look like, what the research confirms, and how to figure out your next step.
Symptoms of Vitamin B12 Deficiency
There are several reasons you might develop a deficiency. Some people simply don’t get enough B12 from their diet. Others have medical conditions — Crohn’s disease, celiac disease, gastritis, pernicious anemia, or alcohol use disorder — that stop the body from absorbing it correctly.
These common symptoms can sneak up slowly, so many people overlook them:
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Weakness
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Tiredness
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Nausea or vomiting
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Diarrhea
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Decreased appetite
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Yellowish skin
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Unintended weight loss
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Sore mouth or tongue
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Numbness or tingling in hands and feet
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Vision problems
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Memory issues
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Confusion
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Trouble walking or speaking
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The Vitamin B12 Deficiency–Cancer Connection
Now let’s get into the big question: can vitamin B12 deficiency be a sign of cancer?
A Deficiency Can Increase Certain Cancer Risks
The American Cancer Society shows that long-term vitamin B12 deficiency may raise the risk for certain cancers, including:
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Stomach cancer
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Breast cancer
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Colorectal cancer
Because B12 plays a key role in DNA production, low levels over time may affect how cells grow and repair themselves.
Some Cancers Can Cause Vitamin B12 Deficiency
Digestive cancers, like those in the stomach or small intestine, can make it harder for your body to absorb B12 in the first place. And certain blood cancers can throw off how your bone marrow makes red blood cells, which ties right back into how your body uses B12.
That’s when the question “can vitamin B12 deficiency be a sign of cancer?” starts to matter, not as a diagnosis, but as a clue that something deeper might be going on.
High B12 Isn’t Always Safe Either
Most people tolerate high B12 well, but balance matters because taking too much can cause:
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Nausea
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Diarrhea or constipation
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Tingling
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Skin breakouts
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Fatigue
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Headaches
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Treatments for Vitamin B12 Deficiency
The good news? Vitamin B12 deficiency is one of the most treatable nutrient issues.
Oral Supplements
Over-the-counter pills can work well for people whose bodies still absorb B12 effectively.
Prescription B12 Injections
If absorption is the problem, like with pernicious anemia or digestive disorders, your provider may recommend weekly or monthly B12 injections.
Dietary Changes
Focus on B12-rich foods, including:
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Meat
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Poultry
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Eggs
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Dairy
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Fortified cereals or plant-based milks
Vegans need supplements because plant foods contain almost no natural B12.
Treating the Underlying Issue
If your deficiency comes from any of the issues below, then the root cause must be addressed for your levels to return to normal:
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Celiac
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Chronic gastritis
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Autoimmune disease
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Alcohol use disorder
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A potential gastrointestinal cancer
If symptoms persist or worsen, it is necessary to investigate whether the deficiency could be a sign of cancer.
RELATED: 5 Incredible Reasons to Start Taking B12
Vitamin B12 Deficiency & the Black Community
This part matters because the numbers don’t lie: the Black community has unique risks related to both B12 deficiency and the cancers linked to it.
Here’s what we know from the American Cancer Society:
Higher Rates of Digestive Issues
Black Americans are more likely to develop conditions like gastritis or H. pylori infection, which can interfere with B12 absorption.
Disparities in Screening
Colorectal cancer screening rates are lower in Black communities, and diagnoses often happen at later stages. If someone is already asking, “Can vitamin B12 deficiency be a sign of cancer?” the slower access to screening makes it even more important to take symptoms seriously.
Dietary Patterns Matter
Many Black households, for cultural or economic reasons, eat fewer foods high in B12, especially as we shift toward more plant-forward diets. That’s not a bad thing, but it does require us to be more intentional about B12 supplements.
Pernicious Anemia Risks
Pernicious anemia is one of the major causes of vitamin B12 deficiency. It is slightly more common in Black women than people realize. But because symptoms mimic stress or aging, it often gets overlooked.
This is why understanding the signs of vitamin B12 deficiency and knowing when it might signal something more serious is crucial for our community’s long-term health.
What to Do if You Have Symptoms
Let’s be clear: having a vitamin B12 deficiency does NOT mean you have cancer. Most people with low B12 do not have a cancer diagnosis behind it.
According to the Mayo Clinic, you should seek medical care if your symptoms come with:
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Ongoing abdominal discomfort
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Rectal bleeding
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Jaundice
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A personal or family cancer history
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A deficiency that doesn’t improve with supplements
Your provider may recommend bloodwork, stool tests, imaging, or endoscopy depending on symptoms.
Frequently Asked Questions: Vitamin B12 Deficiency
Can vitamin B12 deficiency be a sign of cancer?
What cancers are linked to vitamin B12 deficiency?
How long does it take to fix a B12 deficiency?
Can you have B12 deficiency without anemia?
Is it dangerous to ignore B12 symptoms?
The Bottom Line
So, can vitamin B12 deficiency be a sign of cancer? Sometimes, yes. But usually, it’s a treatable condition with many possible causes.
The key? Don’t ignore the signs your body is sending.
If something feels “off,” trust that instinct. Get tested, get answers, and get treated early.
