Can Alli Weight Loss Aid Affect Birth Control?

Alli is a weight loss aid that works by blocking about 25 percent of the fat that you eat. It breaks down and blocks fat absorption in the digestive system, and when combined with a low-fat diet, can be used to effectively lose weight. However, Alli can also interfere with certain medications.

Alli Interference With Meds

• Because Alli causes malabsorption in the digestive tract, there is the possibility that it could block the breakdown and absorption of certain medications. There is no evidence, however, that this is the case with birth control pills.

Birth Control Pills

• According to Alli's website, it does not interfere with the absorption and effectiveness of birth control medication. A clinical trial found that orlistat, the active ingredient in Alli, did not have any effect on women who took birth control pills. In the trial, 20 women took birth control pills and orlistat for 23 days, and there was no evidence of any interference with ovulation suppression from the birth control drugs.

  While alli does not interfere with birth control pills, antibiotics, statins and cholesterol-lowering medication, there is the possibility of it interfering with other types of medication. Speak to your pharmacist or physician if you are concerned about Alli affecting the absorption of other medications.

Vitamin Blocker

• Alli can also block the absorption of some vitamins, so you should take a vitamin supplement at least two hours before or after taking Alli with a meal. Your physician may recommend that you take a vitamin supplement at night, so that it can be fully absorbed.