Some websites that sell medicine can be not state-licensed pharmacies or aren't pharmacies at all; or may give a diagnosis that is not correct and sell medicine that is not right for you or your condition; or won't protect your personal information.
The medicines that sold online can be fake (counterfeit or 'copycat' medicines); can be too strong or too weak, or have dangerous ingredients, or have expired (are out-of-date), or haven't been approved or checked for safety and effectiveness, can be made using non-safe standards, or not safe to use with other medicine or products you use.
The same is true before using any medicine. Every choice to take a medicine involves thinking through the helpful effects as well as the possible unwanted effects.
You need keep an up-to-date, written list of ALL of the medicines (prescription and over-the-counter) and dietary supplements, including vitamins and herbals, that you use--even those you only use occasionally.
You have to know what to do if you experience side effects and when to notify your doctor, and know when you should notice an improvement and when to report back.
Researchers say there are several important variables that affect individual differences in how drugs are metabolized, including race, gender, age, and health conditions. For example, people with kidney or liver disease don't eliminate drugs from their system as well as people who are healthy. Very young children and older people have slower drug metabolism than others, and women may metabolize drugs differently than men in some cases.