Every claim is subject to its own statute of limitations. The statute of limitations places a limit on the amount of time a person has to file a lawsuit. Statutes of limitations vary from state to state, and from claim to claim. The purpose of such limitations is to ensure that claims are brought when evidence is fresh. You are much more likely to end up with a favorable outcome if your injuries are recent and observable.
In most cases, the statute of limitations will begin to run at the time a person suffers an injury. But sometimes it is not reasonable for a person to have discovered that an injury has occurred. In these cases, the statute of limitations does not begin to run until the injury should reasonably have been discovered.
The bottom line is that it is best to call an attorney to discuss your situation as soon as the situation arises. Whether it is a car accident or a drug injury, only an experienced attorney can assess your situation and help you file in a timely manner.