Constipation During Chemotherapy: Causes and What You Can Do

Constipation is a common side effect of many chemotherapy regimens. It can add discomfort to an already challenging treatment journey. Understanding why it happens and how to manage it can help you stay more comfortable and maintain your treatment schedule.

Why Chemotherapy Can Cause Constipation

Chemotherapy itself often isn’t directly “constipating,” but the drugs used alongside it—and the effects they have on your body—can lead to slowed bowel movements. Key factors include:

• Opioid Pain Medications
  • Many cancer patients take opioids (morphine, oxycodone, fentanyl) for pain relief.
  • Opioids bind to receptors in the gut, slowing intestinal muscle contractions and hardening stools.

• Antiemetics (Nausea Drugs)
  • Drugs like ondansetron and granisetron help control nausea but also reduce gut motility.
  • When your intestines move more slowly, waste sits longer in the colon and becomes harder to pass.

• Dehydration
  • Chemotherapy can cause vomiting, diarrhea, or reduced appetite and fluid intake, all of which dehydrate you.
  • Less fluid in your system means drier, firmer stools that are more difficult to pass.

• Dietary Changes
  • Loss of appetite, taste changes, mouth sores, or difficulty swallowing can lead to eating less fiber-rich fruits, vegetables, and whole grains.
  • Low-fiber diets contribute to sluggish bowels.

• Reduced Physical Activity
  • Fatigue, muscle weakness, and treatment schedules may limit your ability to exercise.
  • Physical movement helps stimulate intestinal activity; without it, transit time slows.

• Electrolyte Imbalances
  • Chemotherapy can disrupt sodium, potassium, and magnesium levels.
  • Abnormal electrolytes can impair muscle contractions in the gut wall.

• Nerve Damage (Chemotherapy-Induced Neuropathy)
  • Some agents (taxanes, vinca alkaloids, platinum drugs) can damage peripheral nerves, including those that control bowel function.
  • Impaired nerve signals may slow intestinal muscles.

• Tumor Effects and Surgery
  • Tumors in or near the gastrointestinal tract can physically obstruct or narrow the bowel.
  • Abdominal or pelvic surgery may alter normal bowel anatomy or nerve supply.

How to Prevent and Relieve Chemotherapy-Related Constipation

Managing chemo constipation involves a balanced approach: lifestyle changes, dietary adjustments, and—when needed—medications.

1. Non-Drug Measures

• Hydration
  • Aim for at least 8–10 cups (2–2.5 liters) of fluids daily, unless restricted by your care team.
  • Water, clear broths, herbal teas, and electrolyte solutions help soften stool.

• Dietary Fiber
  • Gradually increase soluble fiber (oats, apples, carrots) and insoluble fiber (whole grains, nuts, green beans).
  • If raw fruits and vegetables irritate your mouth or gut, try cooked, pureed, or blended versions.

• Physical Activity
  • Even gentle walking, stretching, or seated leg lifts can stimulate your bowels.
  • Aim for 10–30 minutes most days, based on your energy level and medical approval.

• Regular Toilet Routine
  • Try to have a bowel movement at the same time each day, ideally 30 minutes after a meal (gastrocolic reflex).
  • Do not rush; give yourself at least 10–15 minutes to relax on the toilet.

• Positioning
  • Elevating your feet on a small stool (“squat” position) aligns your colon for easier passage.
  • Lean forward with elbows on knees and relax your abdominal muscles.

• Abdominal Massage
  • Gentle clockwise massage from the right lower abdomen, up to the ribs, across, then down the left side can help move stool.

2. Over-the-Counter and Prescription Medications

When lifestyle changes alone aren’t enough, several classes of medications can help. Always discuss with your oncologist or palliative care team before starting new drugs.

• Stool Softeners (Surfactants)
  • Docusate sodium (Colace) draws water into stool, making it easier to pass.
  • Works slowly—expect results in 1–3 days.

• Bulk Forming Laxatives
  • Psyllium (Metamucil) or methylcellulose add bulk and moisture.
  • Take with plenty of water. Contraindicated if you have a risk of bowel obstruction.

• Osmotic Laxatives
  • Polyethylene glycol (PEG, MiraLAX), lactulose, magnesium citrate attract water into the bowel.
  • Onset: 1–3 days for PEG, a few hours for magnesium citrate.

• Stimulant Laxatives
  • Senna, bisacodyl stimulate intestinal muscle contractions.
  • Use short-term: risk of cramping and electrolyte imbalance.

• Chloride Channel Activators
  • Lubiprostone (Amitiza) specifically approved for opioid-induced constipation.
  • Increases fluid secretion in the gut and improves motility; shown effective in clinical trials (Chey et al., Am J Gastroenterol 2014).

• Peripherally Acting Mu-Opioid Receptor Antagonists (PAMORAs)
  • Methylnaltrexone, naloxegol block opioids in the gut without affecting pain relief in the brain.
  • Used when conventional laxatives fail (EAPC position statement, Larkin & Cherny, J Pain Symptom Manage 2013).

3. Monitoring and Adjusting

• Keep a bowel diary of stool frequency, consistency (use Bristol Stool Chart), diet, fluid intake, medications, and activity.
• Share this log with your healthcare team; they can tailor your regimen and adjust dosages.

When to Seek Medical Attention

Constipation can usually be managed at home, but certain signs require prompt evaluation:

• Severe abdominal pain or distension
• Vomiting, especially if it’s green or brown (“feculent”)
• No bowel movement for more than 5–7 days despite laxatives
• Blood in stool or black, tarry stools
• Signs of dehydration: dizziness, dry mouth, low urine output

If you experience any of these, please speak to your oncology nurse or doctor immediately.

Tools to Help You Take Charge

You might consider doing a free, online symptom check for to help identify other possible causes of your symptoms and guide you on next steps. This tool doesn’t replace medical advice but can help you prepare questions for your healthcare team.

Final Thoughts

Constipation during chemotherapy is distressing but often manageable with a combination of:

• Adequate fluids and fiber
• Regular physical activity
• Scheduled bowel habits
• Appropriate use of laxatives or prescription agents

Always discuss new treatments or concerns with your oncologist, palliative care specialist, or primary care provider. They can rule out serious complications, adjust your medications, and ensure you maintain the best quality of life throughout your treatment journey.

If you ever feel pain that’s severe, notice alarming symptoms, or your constipation persists despite these measures, please speak to a doctor right away.