Lung cancer can cause diarrhea, but this is rarely due to the condition itself. It is more commonly the result of side effects from cancer treatment.

Lung cancer can result in gastrointestinal symptoms like diarrhea. This is because the condition can alter your immune system and make you more susceptible to infection. However, this is rare and tends to only appear during advanced stages of lung cancer.

The most common cause of diarrhea in those who have lung cancer is often the treatment they are receiving. Many cancer treatments can often cause or worsen diarrhea.

Some treatments for lung cancer can result in side effects such as diarrhea. This includes:

  • chemotherapy drugs, such as docetaxel (Taxotere) and irinotecan (Camptosar)
  • immunotherapy, such as pembrolizumab (Keytruda) and nivolumab (Opdivo)
  • targeted therapy drugs, such as gefitinib (Iressa) and erlotinib (Tarceva)
  • radiation therapy

If your side effects from lung cancer treatment are frequent or worsening, consider speaking with your care team. They may be able to suggest an alternative treatment option.

There are several ways you can manage diarrhea, including:

  • Staying hydrated: If you have diarrhea, it’s important to drink plenty of fluids to avoid dehydration. Try to take small sips of water regularly throughout the day.
  • Eating frequent and small meals: It can be helpful to eat small meals frequently throughout the day. This can give your stomach time to settle and allow you to digest your food slowly.
  • Avoiding triggering foods: Some foods, such as those high in fat and spicy foods, can cause or worsen diarrhea. Try to avoid triggering foods where possible.
  • Getting plenty of rest: Diarrhea can lower your energy, which is why it is important to rest as much as possible until the infection clears.

Diarrhea can often lead to dehydration, which, if left untreated, can be life threatening. If you have diarrhea and feel lightheaded, have a fever of 100.5°F (38°C) or higher, or experience chills, it is important to speak with a doctor immediately.