A just-released study says that Paxil, when taken with the popular cholesterol medication Pravachol, can cause a significantly high rise in blood sugar levels. The results of this study will likely mean the most to diabetics, whose sugar levels are already dangerously high.

“This interaction may affect as many as 1 million Americans who might be on these two drugs and who are getting a bump in their blood glucose that may be unnecessary,” says the lead researcher involved in the study, Dr. Russ Altman, a professor of bioengineering, genetics and medicine at Stanford University. “It’s possible that the blood sugar spike triggered a diagnosis of type 2 diabetes in some patients, and we might have been able to avoid that diagnosis if they hadn’t been on these drugs.”

While neither drug has raised blood sugar on its own, researchers involved in this study made it clear that they can’t explain yet just how the combination causes that effect. It should also be noted that other antidepressants mixed with cholesterol-lowering drugs don’t have that effect, either. This study was published online May 25 in Clinical Pharmacology and Therapeutics. Researchers used data mining to get the information that they needed for their study.

Data mining involves researchers sifting through large databases with the hopes of finding information that can help them mix their data in a new way. For this study, Altman’s team used information collected from the U.S. Food and Drug Administration’s Adverse Event Reporting System, as well as information from Stanford, Harvard and Vanderbilt Universities, to identify the links that normally wouldn’t be put together by physicians who treat the patients. In looking at combined data (that doctors aren’t privy to unless they treat every patient included in the database), the researchers were able to discover 135 non-diabetic patients that were taking both Paxil and Pravachol whose blood sugar rose to 19 milligrams per deciliter once they began their treatment. They also found 104 diabetics whose blood sugar rose on average of average of 48 mg/dl when they were taking the drugs together.