The hamster is weak and may breath heavily but slowly and the body may appear thinner. You can check to see if the hamster is dehydrated by pulling the skin away from the body. If the skin slowly falls back to the body rather than quickly returns to normal the hamster is dehydrated. Give the hamster some water with a tiny bit of sugar and salt in it (using a syringe without the needle to gently syringe some drops of the solution into the side of the mouth). If the dehydration is not due to diarrhoea the feeding of a vegetable high in water content (such as cucumber) will also help.