Is it permissible to combine ruqya with medical treatment?

Not merely permissible. It is what the Sunnah actually prescribes.

The Prophet, peace be upon him, said that Allah sent down no disease without also sending down its cure, and instructed his companions to seek treatment. He used honey, recommended black seed, and underwent cupping. He also recited, and had recitation performed over him.

He did both. There was never a choice being made.

Medicine and ruqya are both means, and both operate only by the permission of Allah. Treating them as rivals introduces a conflict Islam does not contain.

The practical position

• Attend your appointments
• Take what has been prescribed
• Complete the investigations
• Recite daily alongside all of it
• Tell your doctor if you want to; there is nothing to hide

Any practitioner who tells you to stop your medication has disqualified himself. This is not a difference of opinion. Leave, and do not return.