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SYMPTOMS

Constipation or irregularity

Everyday reasons for irregularity, what to ask your doctor to check, and which nutrients have been studied.

Also described as: constipat, irregular, diarrh, loose stool, bowel, not regular

Common everyday causes

Slow transit (too little fiber or fluid)

Without enough soluble fiber and water, stool moves slowly — the commonest cause of constipation and of the bloating that comes with it. No test needed at first. See your doctor if it lasts more than 3 months or comes with bleeding or weight loss.

Gut-bacteria imbalance

Antibiotics, acid reducers, stress and low-fiber eating shift the gut bacteria, which shows up as bloating, gas and irregularity — sometimes skin and mood too. Usually no test is needed. If it lasts more than 4–6 weeks, see your doctor.

Low magnesium

Magnesium relaxes muscles and nerves and is used in hundreds of energy reactions. Diet, stress, alcohol, acid reducers and water pills all lower it. Ask for a red-blood-cell (RBC) magnesium test; serum magnesium misses most low levels.

A food that doesn’t agree with you

Lactose, gluten and fermentable carbs (FODMAPs) are the usual suspects for bloating and irregularity; celiac disease must be tested before going gluten-free. Try 2 weeks without the suspected food. Before cutting gluten, ask for a celiac blood test (tTG-IgA).

An underactive thyroid

The thyroid sets your metabolic pace; when it slows, energy, mood, hair, skin and bowels slow too. It is common in women and after pregnancy, and it needs a doctor, not a supplement. Ask for TSH and free T4 (plus TPO antibodies).

Bacterial overgrowth in the small intestine (SIBO)

Bacteria growing too high in the gut ferment food early, so bloating starts soon after eating. Acid reducers and slow motility raise the risk. It’s treated with prescribed antibiotics, not supplements; fiber can make it worse. Ask your doctor about a SIBO breath test.

If you take certain medicines

GLP-1 medicine: eating less protein and nutrients

GLP-1 medicines cut appetite so much that protein and micronutrients often fall short; fast weight loss also triggers hair shedding. Ask for B12, ferritin and vitamin D tests; aim for 25–30 g of protein per meal.

What’s been studied

• Bacillus coagulans

  For gut balance.

• Magnesium

  For low magnesium.

• Selenium

  For thyroid. Only with a lab result that shows it’s needed.

• Vitamin B12

  For GLP-1 medicine.

• Magnesium

  For slow transit.

apiece asks a few quick questions about irregularity in its quiz to tell these causes apart, and suggests only ingredients studied for the likely ones.

Questions

What can cause irregularity?

Common everyday reasons include slow transit, gut balance, low magnesium, a food reaction, thyroid. A doctor can help find which applies to you.

What tests can help explain irregularity?

Ask your doctor about: No test needed at first. See your doctor if it lasts more than 3 months or comes with bleeding or weight loss; Usually no test is needed. If it lasts more than 4–6 weeks, see your doctor; a red-blood-cell (RBC) magnesium test; serum magnesium misses most low levels; Try 2 weeks without the suspected food. Before cutting gluten, ask for a celiac blood test (tTG-IgA); TSH and free T4 (plus TPO antibodies); Ask your doctor about a SIBO breath test.

Which supplements are studied for irregularity?

Depending on the cause: Bacillus coagulans, Magnesium, Selenium, Vitamin B12, Magnesium. Some only make sense with a lab result (for example iron only when ferritin is low).*

*These statements have not been evaluated by the Food and Drug Administration. This product is not intended to diagnose, treat, cure, or prevent any disease. This page is general information, not medical advice. Check with your doctor or pharmacist before starting a supplement, especially if you take medication, are pregnant or nursing, or have a health condition. Updated 2026-10-21.