As far as I understand, credit card Travel Medical Insurances do not cover pre-existing conditions unless they are stable for a period of time (3 months, 6 months, or 1 year depending on your age). Any change in medication be it a new prescription, an increase or decrease dosage or stopping altogether means a change in the "stable" definition. Any new investigations, tests, any new referrals to specialists will be considered new existing conditions. Reading insurance policies is like reading any boring and long legal documents. Better make sure you understand what is covered and what is not. I think HAL's Platinum CPP (Cancellation Protection Plan) covers any medical expenses upto $10,000 USD pre-existing conditions or not. But $10,000 USD is nothing if you encountered something major. I've also seen people with health issues blindly buying the Travel Insurance their TA handled without understanding the true coverage and thinking they're well covered. Good luck to them!