Given the current double digit inflation in hospital bills, in our view, you should have a cover of at least 25 Lakhs by the age of 35 years. Since you have already crossed 35, you must buy this cover as soon as possible.
Upgrades can be tricky once you have an illness, hence do not depend on upgrading covers at a later age
Ensure there are no financial limits on surgeries/treatments and room rent in your policy.
Ensure you make detailed declarations regarding your health when buying the policy.