In general, Iran is a healthy country to travel in, and you are unlikely to catch any exotic deceases here. The main troubles for tourists are stomach upsets and heat exhaustion. Ask your doctor what medicine should be in your medical kit, and bring them with you. Make sure you are healthy before you start traveling. No vaccinations are required before entering Iran, but your doctor may advise inoculation against hepatitis, malaria, and typhoid.
If you do not feel well, start by consulting with a pharmacist regarding your symptoms in any drugstore. Iranian pharmacist are able to diagnose minor health problems and to suggest appropriate treatment. In case you need a doctor, do not hesitate to contact one. The quality of health care is reasonably high by international standards. Many doctors have received training in the West, and speak basic European languages. In an emergency, summon a taxi to get you to the hospital unless you are accompanied by an Iranian who can call an ambulance. If you get seriously ill, inform your embassy immediately, and for life threatening cases, consider flying back home. Treatment is never free, so it is wise to have travel insurance with health coverage.