How far back does a doctor need to know about what medicine you have been prescribed and used when dealing with a medical issue that has gone on for 3-4 years? does he or she need to know all medicine you have taken for this or just the last year?

Help your doc!: All recent and past medications need to be considered for a complete evaluation, especially for a long term condition.

Info: If you have been treated for the last 3-4 yrs then he needs to know everything you have used for this condition for the last 3-4 years. He will also nee to know your past history as well and what other medication you have used in the past for other issues. Do not forget supplements as well.

Everything.: A medical history should be as complete as possible. I'd imagine it would be most helpful to know everything about your given medical history - all tests and treatments.

Medicine: yes it is much more satisfactory to have a complete knowledge of what you've taken for this condition

Let Doctor decide: The more information you can share with your doctor the better, however doctors are used to sorting problems out with little information also. So let your doctor know everything that you remember and they will work out whether it is needed or not to help you.

Medications: In ideal situation it is good to know everything that has bene prescribed . It helps doctor to decide what should be the next step and what medications to avoid . This prevents repetition of treatment which have caused side affects or haven't worked.

Depends or the issue: In general I would say yes. No sense in prescribing a medication that you have already tried.