Consumer Reports researched the cost of 5 common prescription drugs and found serious differences in the prices being charged for those medicines.

According to the research, online pharmacies associated with major stores were among the cheapest, followed by large department stores like Wal-Mart and Target. The reason is that these companies offer massive discount prescription programs that help bring low cost prescriptions to consumers.

Both Target and Wal-Mart offer discount programs that allow consumers to obtain a 30-day supply of a generic prescription for $4. Other pharmacies, like CVS, K-Mart, and Walgreens, offer prescription club memberships for an annual fee so that customers can purchase low cost medicines.

Not all prescription discounts accept all types of insurance. While some discount programs allow all insurance types, others will limit use by those with Medicaid, Medicare, and some other government based insurance groups.

And not all medications are offered through these discount programs. Most generic prescriptions are on the list, while most name brand medications are not included in the discount program. Checking the pharmacy’s list of included medications is the only consumers know if their medication is covered.