Diarrhea is a very common side effect of antibiotics (medications used to stop or reduce the growth of bacteria). However, some people may also get constipated while taking certain antibiotics.

Constipation is not a very common side effect of antibiotics, but it occurs in some people. You may be more likely to experience constipation while using a class of antibiotics called macrolides. These include medications 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. In some cases, this may result in slower bowel movements, which can lead to constipation.

In one 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 developing stomach-related symptoms, such as constipation, due to a change in gut bacteria as a result of antibiotic use. You may have a higher risk of experiencing 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

There are over 100 trillion microbes that live in your gut, including both beneficial and ‘harmful’ ones. These make up your gut microbiome. A balanced gut microbiome is necessary for proper digestion, immune function, vitamin production, hormone balance, and metabolism.

Despite its benefits, taking antibiotics, especially broad-spectrum antibiotics that target a wide range of bacteria, can disrupt the gut’s equilibrium. This means that some microorganisms will be present in lower numbers, resulting in a lower diversity of bacteria in the gut. 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, leading to stomach-related side effects such as diarrhea, constipation, bloating, gas, and stomach pain.

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.

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:

If you do not treat or manage constipation early, it may lead to complications such as:

• Hemorrhoids or piles 
• Volvulus (twisting of the intestine that can block the bowel)
• Weakened pelvic muscles
• Rectal prolapse (​​part of the rectum slipping out through the anus)