How medications can affect your digestive system and what to do about it

Millions of Australians take prescription medications, over-the-counter medicines or supplements every day. While these treatments play an important role in managing health conditions, some medications can also affect the digestive system and gut health.

Medicines can cause side effects because they do more than target one symptom or condition. This can happen with many products, including prescription medicines, pharmacy medicines, supermarket medicines, vitamins, herbal treatments and complementary and alternative products.

This does not mean the medicine is unsafe or should be stopped. Many side effects of medicines are expected and are mild or temporary. However, it is still important to stay aware of new symptoms, especially if they begin soon after starting a new medicine, changing the dose or adding another treatment.

Digestive changes can also be harder to understand when you take more than one medicine. Prescription medicines, pharmacy products, vitamins, herbal treatments and complementary medicines can all contribute to unwanted effects. Some reactions happen quickly, while others develop gradually over days or weeks.

If you suspect a medicine is affecting your digestive health, talk to your doctor or pharmacist before making changes.

The liver is one of the body's most important digestive organs. It produces bile, a fluid that helps break down fats and supports the absorption of certain nutrients, including vitamins A, D, E, and K.

Beyond its role in digestion, the liver acts as the body's natural filtration system. It processes nutrients absorbed from the digestive tract and helps break down medications, alcohol, and other toxins so they can be safely removed from the body.

Because many medications are metabolised by the liver, some can place additional strain on this organ, particularly when taken long-term or at high doses. In some cases, medications can contribute to drug-induced liver injury (DILI), a condition in which the liver becomes damaged as a result of a prescription medication, over-the-counter medicine, or herbal supplement. While uncommon, DILI is an important cause of liver disease and may require medical assessment and monitoring.

The liver helps process many pharmaceutical products. As such, adverse drug reactions can sometimes involve liver irritation or changes in liver function test results.

Some medicines can affect bowel habits by slowing gut movement, changing fluid balance or altering the gut microbiome. The way your body responds can depend on the medication, dose, treatment duration, existing digestive conditions and overall gut health.

If changes in bowel habits develop after starting a new medication, speak with your healthcare provider. In many cases, symptoms can be managed through changes to treatment timing, diet or lifestyle without stopping the medication altogether.

Yes. Antibiotics such as amoxicillin may cause digestive symptoms in some people, including stomach pain, bloating, nausea or diarrhoea. This does not mean everyone will react the same way, but symptoms should be monitored if they are severe or do not improve.

While antibiotics are designed to eliminate harmful bacteria that cause infections, they can also affect beneficial bacteria that support digestion and overall gut health. This disruption may temporarily alter how the digestive system functions.

For most people, these symptoms are mild and improve once the course of antibiotics is completed and the gut microbiome begins to recover. However, some individuals may experience more significant digestive disturbances, particularly after repeated or prolonged antibiotic use.

Staying hydrated, eating a balanced diet rich in fibre, and following your healthcare provider advice may help support gut health during and after antibiotic treatment. If symptoms are severe, persistent, or worsening, medical review is recommended.

Paracetamol, including brands such as Panadol, is generally less likely to irritate the stomach than some anti-inflammatory pain medicines when used as directed. However, adverse events associated with paracetamol are more serious when the recommended dose is exceeded, especially because of the risk to liver health.

That said, some people may experience mild symptoms such as:

• Nausea
• Stomach discomfort
• Loss of appetite

The more significant concern with paracetamol relates to liver health rather than digestion. The liver is responsible for processing paracetamol, and taking more than the recommended dose can overwhelm this process and cause serious liver damage. The risk is higher with accidental overdose, long-term excessive use, or when paracetamol is combined with alcohol. In fact, paracetamol overdose remains one of the leading causes of acute liver failure in Australia.

While occasional use is generally safe for most people, it is important to follow dosing instructions carefully and seek medical advice if you have existing liver disease or concerns about medication use. If digestive symptoms develop after starting any medication, a healthcare professional can help determine whether the medication may be contributing to the problem.

Your gut and liver are connected through a two-way communication network known as the gut-liver axis. Through this connection, substances produced in the digestive tract travel directly to the liver, where they are processed and monitored.

A healthy gut microbiome helps maintain the integrity of the intestinal lining and supports normal immune function. When the balance of gut bacteria is disrupted, harmful substances may be more likely to enter the bloodstream and reach the liver, potentially contributing to inflammation and other health concerns.

Research continues to show that the gut microbiome can influence various aspects of liver health, including metabolism, immune responses, and inflammation. Because of this close relationship, supporting gut health may also benefit liver function and overall digestive wellbeing.

Maintaining a balanced diet, staying physically active, and managing chronic health conditions can help support both the gut and the liver as part of a healthy digestive system.

While not all medication side effects can be avoided, careful medication management can help reduce the risk of digestive problems.

Strategies that may help include:

• Taking medications exactly as prescribed
• Following instructions about whether a medication should be taken with food or on an empty stomach
• Avoiding missed doses or doubling up on medication
• Informing your healthcare provider about all prescription, over-the-counter, and herbal products you use
• Reporting new or worsening digestive symptoms promptly

Many medications can have gastrointestinal (GI) side effects, and combining multiple medications may increase the risk of adverse effects. In some cases, a healthcare provider may recommend adjusting the dose, changing the timing of treatment, or prescribing an alternative medication if symptoms become difficult to manage.

Some medications are formulated with a protective coating to help reduce irritation as they pass through the stomach and intestine. Others may be available in different forms that are easier to tolerate.

A medication review with a health professional can make treatment safer, especially if you take several medicines or have existing digestive or liver conditions. Always follow your doctor's advice before changing the dose, timing, or frequency of a prescribed medicine.

Liver function tests are blood tests that help assess how well your liver is working and whether there are signs of inflammation or damage. They may be recommended if you have symptoms that could indicate a liver problem or if you take medications that are known to affect liver function.

Your healthcare provider may suggest liver function testing if you experience:

• Persistent nausea or vomiting
• Unexplained fatigue
• Loss of appetite
• Abdominal pain, particularly in the upper right side of the abdomen
• Dark urine
• Pale stools
• Yellowing of the skin or eyes (jaundice)
• Ongoing digestive symptoms without a clear cause

Testing may also be appropriate for people with existing liver disease, heavy alcohol use, metabolic conditions, or those taking certain long-term medications. In some cases, routine monitoring is used to detect liver changes before symptoms develop.

Early assessment can help identify potential problems sooner and guide decisions about treatment, medication use, and ongoing management.

In Australia, the Therapeutic Goods Administration monitors the safety of therapeutic goods, including medicines and vaccines. If a health professional suspects adverse drug reactions or serious adverse events associated with a medicine, they may report adverse events to support medicine safety monitoring.

How long digestive side effects last depends on the medication, dosage, and duration of treatment.

Some symptoms, such as nausea, bloating, or stomach discomfort, may improve within a few days as the body adjusts. Others can persist for as long as the medication is being taken, particularly if it affects gut function or causes a temporary imbalance in the digestive system.

If symptoms are ongoing, worsening, or affecting your quality of life, speak with your healthcare provider. They can determine whether the medication is contributing to the problem and whether changes to your treatment plan are needed.