Health

What happens to your digestion when you take antibiotics

Health · Nov 08, 2025 13:31 · 4 min read

Antibiotics can cause an imbalance of bacteria in the gut, which may contribute to constipation. Credit: urbazon / getty Images

Medically reviewed by Qin Rao, MD Constipation from antibiotics is more common in older adults and people with digestive diseases.Using probiotics and increasing your fiber intake can help provide relief.A doctor may switch your prescription or recommend laxative options to help you pass stool. Taking antibiotics can disrupt your gut bacteria. You ...

Medically reviewed by Qin Rao, MD

Constipation from antibiotics is more common in older adults and people with digestive diseases.
Using probiotics and increasing your fiber intake can help provide relief.
A doctor may switch your prescription or recommend laxative options to help you pass stool.

Taking antibiotics can disrupt your gut bacteria. You may notice digestive side effects like constipation, although it's less common than diarrhea.

Understanding this possible side effect can help you manage discomfort and know when to seek medical attention.

Connection Between Antibiotics and Constipation

Constipation is an uncommon side effect of antibiotics, but it can happen.

You might be more prone to constipation when taking macrolide antibiotics, such as:

Erythrocin (erythromycin)
Biaxin (clarithromycin)
Zithromax (azithromycin)
Zyvox (linezoli)

Researchers have found that antibiotics can cause an imbalance of the bacteria in the gut, which can affect bowel movements. This may result in slower bowel movements, which can lead to constipation.

In a 2024 animal study, researchers found that antibiotics slowed the movement of food through the stomach and colon of mice.

Some people may be at an increased risk of stomach-related symptoms, such as constipation, due to gut bacteria changes from antibiotics.

You may have a higher risk of constipation if you:

Are an older adult
Eat little fiber or have a poor diet
Have existing gut problems like inflammatory bowel disease (IBD)
Use antibiotics for a long time
Are on bed rest
Use other medications that can cause constipation, like opioids

How Antibiotics Affect the Gut Microbiome

Your gut hosts over 100 trillion microbes, both beneficial and harmful. These microbes form the gut microbiome. A balanced microbiome is essential for digestion, immune function, vitamin production, hormone balance, and metabolism.

Taking antibiotics, especially broad-spectrum antibiotics that target a wide range of bacteria, can disrupt the gut's equilibrium. Some microorganisms will be present in lower numbers, which results in a lower gut bacteria diversity.

However, it's not just the good bacteria that are affected, but the "bad" ones as well.

The loss of bacterial diversity can negatively affect the gut. It often leads to stomach-related side effects, such as:

Diarrhea
Constipation
Bloating
Gas
Stomach pain

Managing Constipation From Antibiotics

If you experience constipation, do not stop taking your antibiotics without consulting your healthcare provider. Stopping your antibiotic prescription early could lead to antibiotic resistance, which is when bacteria become insensitive or resistant to antibiotics. This will make antibiotics less effective for you in the future.

Also, discontinuing antibiotics does not always provide relief for constipation. This may be because the time it takes for the gut to recover after loss of diversity varies among individuals. It may take weeks or months for gut equilibrium to be restored, even after antibiotics are stopped.

Here are some methods you can try to manage constipation:

Use Probiotics

Probiotics are live microorganisms that can help maintain the balance of bacteria in your gut. Taking probiotics while taking antibiotics may help support your gut health and improve digestion. However, the research is still mixed on the benefit of probiotics in restoring gut balance.

You can try taking probiotic supplements for a few days to see if you experience constipation relief. If you notice improvement, you can continue taking it as advised by your healthcare provider. You can also try natural probiotics, such as yogurt, sauerkraut, kimchi, and kefir.

Eat More Fiber

Dietary fiber, especially insoluble fiber such as wheat bran, vegetables, and whole grains, can help speed up the movement of food through the digestive tract (stomach and intestines).

Fiber also helps retain water in stools, adding bulk that may help relieve constipation. Fiber supplements, such as psyllium, can also be effective in improving constipation.

If you want to add fiber to your diet, add it slowly. Consuming too much fiber in a short time can increase the risks of other stomach-related side effects, such as gas, bloating, and stomach cramps. Also, drink plenty of water to aid in smooth bowel movements.

Take an Over-the-Counter Medication

Over-the-counter (OTC) laxatives (medicines used to increase bowel movements) can provide short-term relief for constipation. Examples include:

Bulk-forming agents: Metamucil (psyllium), FiberCon (polycarbophil), and Citrucel (methylcellulose)
Stool softeners: MiraLAX (polyethylene glycol), Milk of Magnesia (magnesium hydroxide)
Osmotic agents: Colace or Correctol (docusate)

OTC medications for constipation should not be used for a long time. If you still feel constipated after a week of use, see a healthcare provider. If you have severe stomach pain, nausea, or vomiting, do not use laxatives without a go-ahead from a healthcare provider.

Drink Enough Water

Ensure you are drinking enough water and staying hydrated to prevent worsening the constipation.

If you are taking more fiber, you will need to drink more water. Poor hydration can lead to the hardening of stool instead of providing relief.

Aim to drink about 8 to 10 cups (2 to 2.5 liters) of fluids daily. Water is the simplest form of hydration, but other beverages, like coffee, tea, and fruit juice, count towards your daily intake.

Be Physically Active

If possible, try to move your body. Even gentle movement can help improve constipation. Exercise can help your colon move waste out faster. It can also help move food, gas, and stool along your digestive tract.

When To Talk to Your Healthcare Provider

If you are constipated while taking antibiotics, your healthcare provider may first recommend lifestyle changes, such as adding more fiber to your diet, drinking water, and exercising more.

Your healthcare provider may switch your antibiotics to a different class if possible. They may also prescribe OTC laxatives or, in more severe cases, suppositories or enemas.

See your healthcare provider immediately if you notice symptoms like: