FDA Warns of Kidney Risks with Alli, Over-the-Counter Weight Loss Drug

The U.S. Food and Drug Administration (FDA) has updated the label for Alli, the only over-the-counter weight loss medication in the U.S., to include warnings about rare but severe kidney-related side effects, according to a March 2024 FDA announcement. The revised label now alerts users to risks such as acute kidney injury, kidney stones, and oxalate nephropathy, a condition where calcium oxalate crystals damage kidney tubules.

What Are the New Warnings About Alli?

The FDA’s updated label for Alli’s 60 mg capsules, approved on March 20, 2024, explicitly warns that the drug may cause kidney damage. Consumers with a history of kidney disease or kidney stones are advised to consult a healthcare provider before use. Users are also instructed to stop taking Alli immediately if they experience symptoms like back or groin pain, blood in the urine, painful urination, or leg swelling, which could indicate kidney complications.

Acute kidney injury, defined as a sudden loss of kidney function, can be fatal if untreated, the FDA noted. The agency emphasized that the risks are rare but serious, adding to existing warnings against use by individuals with organ transplants or those taking medications for diabetes, clotting, or thyroid conditions.

Why Is This Significant for Users?

Alli, the over-the-counter version of orlistat, has been available since 2007 and is the first and only OTC weight loss drug in the U.S. Since its introduction, approximately 40 million people have used orlistat in its prescription (Xenical) or OTC (Alli) forms since its 1999 approval, according to the FDA. Despite its long availability, the new warnings highlight ongoing concerns about its safety profile.

Medical experts, including the Mayo Clinic and the U.K.’s National Health Service (NHS), have previously advised against using Alli without medical supervision. Critics point to risks such as vitamin deficiencies, gastrointestinal issues, and potential organ damage, as noted by Dr. Sidney Wolfe of Public Citizen’s Health Research Group, who told ABC News, “These drugs have the potential to cause significant damage to multiple critical organs, yet they provide meager benefits in reducing weight loss in obese and overweight patients.”

How Does Alli Compare to Modern Weight Loss Treatments?

Alli works by blocking the absorption of dietary fat, a mechanism distinct from GLP-1 receptor agonists like Wegovy, Ozempic, and Zepbound, which suppress appetite. While Alli’s weight loss results are generally modest, it played a pivotal role in normalizing the use of pharmaceuticals for weight management. However, the rise of GLP-1 drugs has shifted focus toward more effective but costly treatments.

As of late 2025, about 1 in 8 U.S. adults were taking a GLP-1 drug, according to a KFF poll, doubling the 2024 figure. This trend underscores the evolving landscape of weight management, with Alli now facing renewed scrutiny over its safety despite its historical role.

What Should Users Know?

Consumers using Alli should remain vigilant for kidney-related symptoms and seek medical advice if concerns arise. The FDA’s updated label also reinforces existing precautions, such as avoiding the drug for those with gallbladder issues, pancreatitis, or certain medication interactions.

While the agency acknowledges the drug’s availability without a prescription, it emphasizes the importance of consulting healthcare providers. “The FDA’s action reflects a commitment to ensuring patients are fully informed about potential risks,” the agency stated in its March 2024 update.