Generic medicines contain the same active ingredient as the brand-name versions and usually cost much less. For that reason, many patients now buy generic medicine online, from eye drops such as bimatoprost to weight loss capsules such as orlistat. A little care goes a long way.
Start with a prescription: a valid prescription is required for every order of a prescription medicine. A careful store will ask for it. Avoid any website that does not ask for one.
Look closely at the product: the active ingredient, the strength and the pack size should be easy to find. Generic tablets may look different from the brand you know, and that is expected.
To read a fuller guide, this guide explains what to look for.
A few examples: bimatoprost eye drops are used once here a day in the evening, and you should wait five minutes between different drops. Orlistat 120 mg is taken with meals that contain fat and works best with a low-fat diet, plus a multivitamin at bedtime.
On delivery, compare the pack with your prescription and keep the leaflet. Tell your doctor which product you are taking.
There is more detail in this article.
This is general information, not medical advice. Always check with your doctor before starting a new medicine.