As of 2018, the U.S. Food and Drug Administration (FDA) still found sibutramine in over 700 diet supplements marketed as "natural", "traditional", or "herbal remedies".

[16] In 2010, the FDA noted the concerns that sibutramine increases the risk of heart attacks and strokes in patients with a history of cardiovascular disease.

The following side effects are infrequent but serious and require immediate medical attention: cardiac arrhythmias, paresthesia, mental changes (e.g., excitement, restlessness, confusion, depression, rare thoughts of suicide).

The concomitant use of sibutramine and monoamine oxidase inhibitors (MAOIs, such as selegiline) is not indicated, as it may increase the risk of serotonin syndrome, a somewhat rare but serious adverse drug reaction.

Despite a 2002 petition by Ralph Nader-founded NGO Public Citizen,[32] the FDA made no attempts to withdraw the drug, but was part of a Senate hearing in 2005.

[33] Similarly, in 2004, David Graham, FDA "whistleblower", testified before a Senate Finance Committee hearing that sibutramine may be more dangerous than the conditions it is used for.

[34] Between January 2003 and November 2005, a large randomized-controlled "Sibutramine Cardiovascular OUTcomes" (SCOUT) study with 10,742 patients examined whether or not sibutramine administered within a weight management program reduces the risk for cardiovascular complications in people at high risk for heart disease and concluded that use of silbutramine had a RR 1.16 for the primary outcome (composit of nonfatal MI, nonfatal CVA, cardiac arrest, and CV death).

[36] On January 21, 2010, the European Medicines Agency recommended suspension of marketing authorizations for sibutramine based on the SCOUT study results.

[15] On October 8, 2010, the FDA recommended against continued prescribing because of unnecessary cardiovascular risks to patients, asking Abbott Laboratories to voluntarily withdraw.

[31] Abbott announced the same day that it was withdrawing sibutramine from the US market, citing concerns over minimal efficacy coupled with increased risk of adverse cardiovascular events.

[38] On December 22, 2008, the United States Food and Drug Administration issued an alert to consumers naming 27 different products marketed as “dietary supplements” for weight loss, that illegally contain undisclosed amounts of sibutramine.

[39][40] In March 2009, Dieter Müller et al. published a study of sibutramine poisoning cases from similar Chinese "herbal supplements" sold in Europe, containing as much as twice the dosage of the legally licensed drug.

[42] In January 2010, a similar alert was issued for counterfeit versions of the over-the-counter weight loss drug Alli sold over the Internet.

"[45] In October 2010 the MHRA in the UK issued a warning regarding "Payouji tea" and "Pai You Guo Slim Capsules" which were found to contain undeclared quantities of sibutramine.

[51] In a 2018 study the FDA found synthetic additives including sibutramine in over 700 diet supplements marketed as "natural", "traditional" or "herbal remedies".