Here it depends on the ailment. For influenca, headaches, or backache - a common problem with me, paracetamol is the off-the-shelf drug I find helpful. In fact I found this very helpful when I was in Singapore and in San Diego, when I felt something coming on. Paracetamol, which I bought at a nearby drugstore, kept me out of the hostel bed during the day. Lately, after a severe back attack, my pharmacist reccommended ibuprofen, either as a pill or as a gel rub. Very effective. But all other ailments I visit my GP. For infections, antibiotics can only be prescribed by a Doctor here in the UK, as with codeine, when pain becomes too severe for off-the-shelf medicine.
To answer your question, If I'm unwell, I visit the Doctor. Always. Not a gay website forum!