According to national health policy, a subcentre caters to population in hilly and tribal areas –
Sub-centre 

The sub-centre is the peripheral outpost of the existing healthy delivery system in rural areas.
They are being established : -


One sub-centre for every 5000 population in general.
One sub-centre for every 3000 population in hilly, tribal & backward area.
3000
5000
1000
2500