Skip to content

Weight Loss & Diet Plans

Font Size

Alli: Everything You Need to Know

When Shouldn’t I Take Alli?

Always tell your doctor about all the medications you’re taking. Alli can interact with certain drugs, affecting their levels or how they work in your body, which could lead to life-threatening consequences. Check with your doctor if you’re taking warfarin (a blood thinner), diabetes or thyroid medications, or other weight-loss drugs. In some cases, your dosages may need to be adjusted.

Don’t take Alli if:

Side Effects of Alli

Loose stools and other bowel movement changes are the most common side effects of Alli. Symptoms typically occur during the first few weeks of treatment and then go away. However, they may continue.

Tell your doctor if you have any of the following symptoms and they become severe or do not go away:

  • Difficulty controlling bowel movements
  • Loose, frequent stools
  • Oily or fatty stools
  • Oily spots on undergarments
  • Stomach or rectum pain
  • Passing gas more often
  • Urgent need to have a bowel movement
  • Anxiety
  • Changes in your menstrual cycle
  • Headaches

Emergency Side Effects of Alli

Call 911 or your doctor immediately if you develop any of these symptoms:

  • Difficulty breathing
  • Difficulty swallowing
  • Hives or itching
  • Stomach pain that is severe or does not go away


Alli has been linked to severe liver injury in rare cases, though it has mostly occurred in those taking the prescription-strength dose (Xenical). Stop taking Alli and call your doctor immediately if you develop any of these possible signs of liver damage:

  • Dark urine
  • Fatigue
  • Fever
  • Light-colored stools
  • Loss of appetite
  • Severe, persistent itching
  • Weakness
  • Vomiting
  • Yellowing of the skin or eyes (jaundice)

WebMD Medical Reference

Reviewed by Kimball Johnson, MD on October 13, 2012
1 | 2

Today on WebMD

measuring waist
4 tips for shedding yours.
apple cider vinegar
Does it have health benefits?
Chocolate truffle
For weight loss, some aren’t so bad after all.
woman holding red dress
24 simple, practical tips.
woman shopping fresh produce
butter curl on knife
eating out healthy
Smiling woman, red hair
What Girls Need To Know About Eating Disorders
fat caliper

Special Sections