Can Vitamin B12 Cause Diarrhea: Does It Make You Poop?

Whether for DNA synthesis, energy production, or supporting the proper central nervous system function, your body requires sufficient amounts of vitamin B12 daily.

While it’s not a vitamin we hear much about unless a deficiency is present, specific populations are at higher risk of a deficiency than others. And despite being found in many foods, a B12 insufficiency or deficiency is relatively common.

Just how come? It’s estimated that roughly 20% of people over 60 in the United States and the United Kingdom are deficient in vitamin B12⁽¹⁾.

Because the ability to effectively absorb B12 decreases with age, it’s more common in older people - but that doesn’t mean people of all ages can’t have it.

Whether you’re supplementing to mend a deficiency or to stay on top of your intake, most people won’t experience any side effects from B12.

But for some people, B12 can cause gastrointestinal disruption that lands you in the bathroom. While it may not be the most popular topic of conversation for the table, we’re breaking down the details on vitamin B12 and pooping.

What Is Vitamin B12?

Vitamin B12, also called cobalamin, is part of eight water-soluble B vitamins that must be obtained through diet; the body can’t synthesize them endogenously.

It’s found in high concentrations in animal products, especially red meat, and is essential for red blood cell formation, DNA synthesis, brain development, and nervous system function. It’s also involved in synthesizing fatty acids and myelin via its role as a co-enzyme⁽²⁾.

For most people, hitting their intake of B12 is easy, but for those who follow a vegetarian or vegan diet diet, where does B12 come from? Besides nutritional yeast and certain fortified foods, B12 has to come through supplementation.

We’re not going to get into the nitty gritty of B12, but know that its absorption isn’t as straightforward as other nutrients. For B12 to be absorbed, it requires a protein called intrinsic factor (IF), which is secreted by the stomach’s parietal cells⁽³⁾.

The small intestine houses IF receptors that bind B12 to create a complex, allowing it to be absorbed through the intestinal lining and into systemic circulation.

But whether you’re not consuming enough through diet or not absorbing it properly, a B12 deficiency can spell trouble in several areas - including digestive problems.

Can Vitamin B12 Cause Constipation?

Vitamin and mineral deficiencies probably don’t make it onto your radar of things that can cause constipation; for most people, lack of fiber is the culprit.

But contrary to popular thought, low B12 might leave you straining.

Consuming sufficient essential nutrients is key to optimizing body function, but low levels of vitamins, especially B vitamins, can interfere with how your body absorbs food and how well your gastrointestinal tract functions.

Proper gastrointestinal motility is required for bowel movements, and if that’s not happening, constipation will likely result. The exact mechanism isn’t known, but constipation and fatigue are two common symptoms of low B12.

Related Post: Best Probiotic for Constipation

Why Does Vitamin B12 Cause Diarrhea?

If you’re experiencing chronic diarrhea, it could signify that you’re low in vitamin B12.

While low B12 rarely triggers diarrhea or other gastrointestinal issues directly, they’re usually a symptom of a more complex problem like B12-deficiency anemia or Crohn’s disease. Conditions like celiac disease can also affect vitamin B12 absorption and lead to gastrointestinal issues.

Here’s how these conditions can influence bowel function:

B12 deficiency anemia and red blood cell formation

This is a condition whereby your body doesn’t produce enough healthy red blood cells, which are required to transport oxygen to tissues throughout the body. Without sufficient oxygen, your tissues and organs can’t function properly.

B12 deficiency anemia is tough to diagnose because it doesn’t always present with apparent symptoms. For most people, it starts with the typical anemia symptoms - fatigue, pale skin, shortness of breath, etc, and progresses to more neurological symptoms as the condition worsens.

Symptoms may vary, but commonly you’ll see things like:

• Muscle weakness
• Numbness or tingling feeling in hands and feet
• Difficulty walking
• Nausea
• Decreased appetite
• Weight loss
• Irritability
• Lack of energy or tiring quickly (fatigue)
• Diarrhea

Crohn’s disease

Crohn’s disease is a recurring systemic inflammatory bowel disease that primarily affects the gastrointestinal tract but can also have extraintestinal manifestations and influence immune function⁽⁴⁾.

Because Crohn’s causes inflammation of the intestinal tract, it not only interferes with B12 absorption but can cause more severe symptoms like arthritis, skin problems, fevers, rectal bleeding, and abdominal pain.

That said, diarrhea isn’t the direct result of a B12 deficiency in Crohn’s disease. Still, as the problem worsens from malabsorption, it can lead to diarrhea as a symptom of B12 deficiency anemia.

Ulcerative colitis

Along with Crohn’s, ulcerative colitis (UC) is another inflammatory bowel condition that results in the intestines becoming inflamed; pain ulcers develop in the lining of the colon (large intestine) and commonly lead to diarrhea as a symptom⁽⁵).

Ulcers and inflammation result in many symptoms of Crohn’s, but the cause of bloody diarrhea with UC is due to the inflammation in the colon, causing frequent trips to the loo.

And because ulcerative colitis interferes with metabolism and absorption of food, it can interfere with B12 absorption and result in a deficiency.

How Much Vitamin B12 Do You Need?

Whether you follow a plant-based diet or not, getting enough B12 can be challenging - especially when other factors influence how well it’s absorbed. If you aren’t keen on stressing about nutrient deficiencies, cover your bases with Performance Lab® NutriGenesis® Multi.

It’s a state-of-the-art multivitamin using nature-identical vitamins and minerals for optimal absorption and bioactivities.

Customized to each gender’s specific needs, Multi supports overall health and well-being, hormones, and daily performance - all in just four vegan capsules daily. It’s clean, effective, and simple to fill nutritional gaps in the diet.

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If you're looking for comprehensive coverage of the full B vitamin spectrum, Performance Lab® B-Complex supplement is a smart choice.

It delivers advanced, plant-based NutriGenesis® B vitamins to support energy production, brain function, and mood.

Stacked with choline and inositol for enhanced synergistic effects, this supplement ensures you get the essential nutrients needed for overall cell health and performance.

Performance Lab® B-Complex is especially beneficial for anyone dealing with chronic stress, excess caffeine consumption, or intense physical activity. All of these factors may contribute to increased demands for B vitamins.

Our B-Complex supplies a research backed dosage in just one capsule a day.

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