They will check to see if you have any highly infectious bloodborne diseases like hepatitis or HIV/AIDs and also they will check for TB - as far as I'm aware those are the diseases that will get u denied a residence permit and even entry into the country. It may be a concern to you, but high BP and Cholestrol won't be what the authorities here are concerned in keeping an eye on...But I know good doctors here who may be able to help you once you get to Qatar.