Are medical insurance and social security paid at the same time?

No, pension insurance is the same as personal ID card, and one person can only pay one copy.

At present, China's social insurance has not reached the national network, and it is possible for a person to open an account in two different cities and pay medical and social security at the same time. However, the policy of social medical insurance is that everyone can only enjoy medical insurance benefits once, that is, they can't enjoy reimbursement twice at the same time, so it is useless to buy it twice and only reimburse it once.

So even if two different cities pay medical insurance and social security at the same time for some reason, you can't enjoy two old-age insurances when you reach retirement age. So if two cities pay two insurances at the same time, they will either merge (unlikely) or one of them will be returned to you.

Note: One of them can only be surrendered if you retire or meet the conditions for surrender. So if two different cities pay insurance at the same time, you need to stop paying one insurance.

Further reading: How to buy insurance, which is good, and teach you how to avoid these "pits" of insurance.