Does Tums Cause Dark-Colored Stool?
No, calcium carbonate (Tums) does not typically cause dark-colored stools. Calcium carbonate is a white compound that, if anything, may lighten stool appearance rather than darken it 1.
What Tums Actually Does to Your Stool
- Calcium carbonate appears as white material in the gastrointestinal tract and has been documented coating the stomach and colon in cases of excessive intake 2
- The most common stool-related side effect is constipation, not color change, as calcium carbonate is more likely to cause constipation and bloating compared to other calcium supplements 3, 4
- In intestinal bypass patients, calcium carbonate actually reduced stool water content and frequency, demonstrating its constipating rather than darkening effect 5
Important Caveats About Stool Color Changes
If you're experiencing dark stools while taking Tums, consider these alternative explanations:
- Iron supplements (often taken alongside calcium) are a common cause of black or dark green stools
- Gastrointestinal bleeding produces dark, tarry stools (melena) and requires immediate medical evaluation
- Bismuth-containing products (like Pepto-Bismol) cause black stools
- Certain foods (blueberries, black licorice, dark leafy greens) can darken stool color
Clinical Considerations for Tums Use
- Calcium carbonate requires gastric acid for absorption, so it should be taken with meals 3, 4
- Doses should be divided to 500 mg elemental calcium or less per administration to maximize absorption and minimize gastrointestinal side effects 3, 4
- Excessive intake can cause equipment malfunction during colonoscopy due to white coating material 2
- Do not exceed 2,000-2,500 mg of total elemental calcium daily from all sources 4