When it’s time to refill your next prescription, it may pay to shop around for the best price.

According to HealthDay, a new survey has discovered the prices of prescription drugs can vary by $100 or more for the same drug from store to store, even within the same chain.

The survey also found that consumers are less likely to consult with pharmacists about the drugs they’re using than they were in the past, which can lead to serious consequences in terms of drug interactions, HealthDay said.

“More people are paying a higher percentage of out-of-pocket expenses for their prescriptions than they did in 2002,” said Tod Marks, senior editor at Consumer Reports magazine, which conducted the survey.

“We found that there was a significant price difference, not only for the same drug at different stores, but there were price differences within the same chain and the online price,” Marks said. “Sometimes those prices can be significantly different.”

Consumer Reports called 163 pharmacies nationwide to determine price differences for four prescription drugs—three name brand medicines and one generic.

They discovered the price for a three-month supply of the urinary incontinence drug Detrol ranged from $365 to $551. The price for Plavix, a drug that prevents blood clots, ranged from $382 to $541. Prices for Levoxyl, a treatment for hypothyroidism, varied from $29 to $85. And the costs for the generic osteoporosis drug alendronate ranged from $124 to $306, HealthDay said.

The researchers found that Costco was the cheapest source for the four drugs, while Walgreens and Rite-Aid were among the most expensive. The survey also discovered that consumers shouldn’t rule out independent drug stores, even though they may not be the cheapest because their prices are competitive.

The findings of the study were published in the June issue of Consumer Reports.