I'm wondering if the OP meant when should a diabetic begin using meds to manage blood sugar? If so, some people are able to manage Type 2 diabetes with just diet and exercise and this should always be the first approach. If you are able to maintain target range blood sugars this way, great! Just continue testing periodically to make sure it is still working, and to see how certain foods affect your blood sugar. When this no longer works and numbers are too high then it's time to talk to your doctor about some oral meds.
It will depend on what the medicine is and your doctor's instructions.
More information please. We can't help you based on what you've asked.
YOu can also ask your pharmacist. They are usually very helpful on clarifying medication instructions.