I don't have a Medical Aid. May I still claim for medical expenses like GP visits, dental etc?

You can definitely claim for these expenses provided you can demonstrate to SARS that you paid for them. These expenses are called, "qualifying medical expenditure" and would be allowed as a deduction with certain limits.

Things like doctors, dentists, specialists, over the counter medication, prescribed medication etc Anything a normal medical aid would cover if you had full coverage can be claimed.