High Pottasium

Hi

my 3 year old son had a blood test today and the reslts came back the same day saying his potassium is raised, they want him to have another test tomorrow. What does this mean if it's still high? Whats the cause? He doesnt eat anything that could make it high, im so scared and worried what is wrong with him. The reason he was sent for a test int he first place is because he did wee very often he started to go with out weeing up to 24 hours sometimes and when he did he usually done a lot. I just dont know what could be wrong.