Vitamin B Complex and Yellow Stools: What’s the Link?
Diet & NutritionNutrients & Supplements

Can Vitamin B Complex Cause Yellow Stools?

Can Vitamin B Complex Cause Yellow Stools?
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Updated on August 7, 2025
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B vitamins help your body produce or use the energy from your diet. They also help produce red blood cells.

Some people take supplements to top up low B vitamin levels. B complex supplements provide a mixture of different B vitamins.

Because B vitamins also affect your metabolism, taking excess vitamins in a B complex supplement may upset your digestive system and cause changes in your stools.

Yellow stools may also indicate gastrointestinal problems, a possible side effect of taking too much vitamin B. If the problem persists, see your doctor.

Why Can Poops Turn Yellow?

Doctors consider a shade of brown to be a normal poop color. However, changes in your diet can change the color and consistency of your stools.

For example, eating lots of leafy green vegetables or products with green food coloring can cause your stools to be green.

Likewise, stools can sometimes be yellow. Foods high in beta-carotene, such as carrots, squash, and sweet potatoes, or yellow spices, like turmeric, can make stools yellow. These foods contain natural pigments called carotenoids that have this effect.

A yellow stool color can also develop due to the presence of fat in the stool, which may occur if you eat too many fatty foods. The protein gluten, present in many cereals and breads, can also cause yellow stool if you have problems digesting it.

Other conditions that can cause issues with fat absorption include Crohn’s disease, pancreatitis, liver disease, exocrine pancreatic insufficiency (EPI), or cancers of the pancreas, liver, or bile duct.

You might also have yellow diarrhea after gallbladder removal surgery. You can live without a gallbladder. However, bile, an essential digestive fluid for breaking down fats, now moves straight from the liver to the intestines. This means the intestines may not be able to absorb all of the bile immediately after surgery. In turn, stools may contain more bile, turning yellow.

Can Vitamin B Complex Change Your Stool Color?

Stools often change color in response to supplemental vitamins and minerals. This is normal, but be sure to speak to a doctor if you also experience abdominal pain.

In general, diarrhea may also appear yellow because of how fast it’s moving through your intestinal tract.

But can B complex make poop yellow specifically? Perhaps indirectly if you take excessive amounts. This might be due to the side effects of niacin, or vitamin B3. If the vitamin B complex supplement you take includes niacin, check the label for the dosage.

The recommended dietary allowance of niacin ranges from 14 to 16 milligrams (mg) a day, increasing to 18 mg during pregnancy and 17 mg during lactation. If you take 1,000 to 3,000 mg of niacin daily, side effects can include diarrhea, nausea, heartburn, and abdominal pain. Taking niacin in large amounts can also cause liver damage, which can be very serious.

Liver damage can cause pale, yellow stools, as bile salts from the liver usually contribute to the standard brown color of stools. If an issue like cirrhosis, or liver scarring, affects the release of bile salts, it may mean your poop is paler.

Although rare, liver damage can occur after taking too much of any supplement, not just niacin.

Niacin can also cause bloating, burping, facial redness, and increased gas. If you experience allergic reactions or have symptoms of high blood sugar, like increased thirst and fatigue, blurry vision, or increased urine output, seek prompt medical attention.

A healthcare professional may recommend getting blood tests every six months to check liver function and blood glucose levels for people taking vitamin B3 for an extended period.

Other B Complex Side Effects and When to See a Doctor

Outside of stool changes, you may experience other side effects when taking B complex supplements, including:

  • Diarrhea
  • Facial redness
  • Extreme tiredness
  • Headache
  • Nausea
  • Upset stomach
  • Bright yellow pee

However, unless these are persistent or interfere with daily life, you may not need to see a healthcare professional if you experience these effects.

Other effects require reporting to a medical team as soon as possible, including:

  • An allergic reaction, including rashes, itching, hives, and a swollen face, tongue, throat, or lips
  • High blood sugar symptoms
  • Other liver damage symptoms, including pain in the upper-right abdomen, appetite loss, dark yellow urine, a yellow tint in the skin or eyes known as jaundice, and feeling unusually weak or tired
  • Tingly, numb, or painful feet
Following a balanced diet means that most people are unlikely to develop a B vitamin deficiency. Ask your physician to check the cause of your yellow stools, and discuss taking any supplement with a healthcare professional before starting.

The Takeaway

  • Taking a B complex supplement may alter stool color if you take excessive amounts due to its adverse impact on the liver.
  • If you have stool changes and other liver damage symptoms, such as upper-right belly pain, extreme fatigue, and jaundice, promptly discuss these with a healthcare provider.
  • Other common side effects of B complex supplements include diarrhea, bright yellow urine, facial redness, and nausea, but these are often not concerning unless persistent or severe.
  • Always speak to a healthcare professional before starting to take a vitamin or mineral supplement.
EDITORIAL SOURCES
Everyday Health follows strict sourcing guidelines to ensure the accuracy of its content, outlined in our editorial policy. We use only trustworthy sources, including peer-reviewed studies, board-certified medical experts, patients with lived experience, and information from top institutions.
Resources
  1. B Vitamins. MedlinePlus. September 23, 2021.
  2. Rana P et al. Prescribing vitamin B complex: Need for reassessment. Indian Journal of Medical Research. December 2021.
  3. Stool color: When to worry. Mayo Clinic. October 10, 2024.
  4. 4 Things That Cause Yellow Diarrhea. Cleveland Clinic. March 5, 2025.
  5. Vitamin B Complex Tablets or Capsules. Cleveland Clinic.
  6. Niacin. Office of Dietary Supplements. November 18, 2022.
  7. Stools - pale or clay-colored. Mount Sinai.
  8. Liver Damage Caused by Supplements Is Becoming More Common. Weill Cornell Medicine. June 25, 2025.
  9. Niacin Capsules and Tablets. Cleveland Clinic.
  10. Vitamin B complex. University of Rochester.
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Yuying Luo, MD

Medical Reviewer

Yuying Luo, MD, is an assistant professor of medicine at Mount Sinai West and Morningside in New York City. She aims to deliver evidence-based, patient-centered, and holistic care for her patients.

Her clinical and research focus includes patients with disorders of gut-brain interaction such as irritable bowel syndrome and functional dyspepsia; patients with lower gastrointestinal motility (constipation) disorders and defecatory and anorectal disorders (such as dyssynergic defecation); and women’s gastrointestinal health.

She graduated from Harvard with a bachelor's degree in molecular and cellular biology and received her MD from the NYU Grossman School of Medicine. She completed her residency in internal medicine at the Icahn School of Medicine at Mount Sinai, where she was also chief resident. She completed her gastroenterology fellowship at Mount Sinai Hospital and was also chief fellow.

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