Alli is a weight loss medication that’s approved by the U.S. Food and Drug Administration for over-the-counter sale. Mixing weight loss medications with similar medications isn’t recommended, cautions the Weight-control Information Network, or WIN, an information service of the National Institutes of Health. Taking additional weight loss supplements can be dangerous, too. However, you can take Alli with one specific supplement — and in fact, this is a must-do if you use this particular diet aid.

Alli Primer

Alli is simply a reduced-strength version of the prescription weight-loss medication, Xenical, or orlistat. Orlistat works quite differently than other anti-obesity drugs, which suppress your appetite. A lipase inhibitor, Alli blocks modest amounts of dietary fat that your body normally absorbs. Unlike most prescription weight-loss drugs, which can safely be taken for only three months, you can use orlistat for up to a year.

Recommended Supplement

Alli doesn’t just block dietary fat — it also reduces absorption of fat-soluble vitamins, such as vitamins A, D and E, says Mayo Clinic doctor Donald Hensrud. You do need to take a vitamin supplement each day while using Alli to get adequate amounts of essential nutrients. This supplement should not be taken at the same time you take Alli, however — take it two hours before or after your Alli dose, advises WIN.

Weight Loss Supplements

Other nonprescription weight loss aids aren’t approved by the FDA as drugs: dietary supplements. Because they’re classified as such, you have no assurance that they’re safe or effective to use. Nor can marketers of non-FDA-approved weight loss supplements expressly claim that their product will cause you to lose weight. Some supplements are dangerous even when taken on their own, points out MayoClinic.Com. Natural weight loss supplements containing ephedra and country mallow, or heartleaf, were banned by the FDA due to safety issues. Another ingredient used in weight loss supplements, bitter orange, has also raised safety concerns.

Bottom Line

With the exception of a recommended vitamin supplement, all others are off-limits. If you take Alli, MayoClinic.Com warns that you should not take any other prescription or nonprescription medicines, including herbal supplements, without talking to your doctor about it first.

Best Results

Although Alli and other anti-obesity medications are helpful, they’re not a magic bullet for weight loss, according to WIN. Making changes in your eating habits and lifestyle are essential to lose weight and keep it off permanently. The manufacturers of Alli designed this weight loss aid to be used in conjunction with a low-calorie, low-fat diet and exercise program for optimal results. Eat more than 15 g of fat per day and you risk unpleasant side effects, such as diarrhea, gas, oily anal discharge and frequent, pressing bowel movements, cautions Hensrud.