To apply for a residence permit, you must have health insurance which meets minimum coverage requirements, and which is valid in Turkey. You must include a copy of your policy in the package you submit with your residence permit application.
Why Turkish Private Health Insurance Might Be Your Best Option
Private health insurance from a foreign country will only accepted if the provider has an office in Turkey
SGK insurance can only be applied for after you have legally resided
Health insurance is required for anyone who wants to get a residence permit in Turkey. For many foreigners, health insurance provided by a private Turkish company is the best solution.