Hello dear, Thank you for writing. In my opinion your child might have a viral infection, which is very common among children in this age. That would explain the decrease of urination: the body is already losing water through diarrhoea, therefore the kidney does not need to produce urine. Diarrhoea is characterised not only by the loss of water, but also of other elements like: potassium, sodium, chloride, different nutrients etc. In order to help the recovering, the best way is to drink oral rehydration solutions, that contain the above mentioned elements in specific concentration. You can find such preparations in pharmacy, and they come in different brands and flavours. Consult with your pharmacist about the options. If it seems like the oral fluids are not rehydrating his body (if the headache and malaise persists, if he still cannot urinate normally) or he can t comply with oral rehydration (ie vomits after drinking the solution), consult with your physician for the possibility of intravenous rehydration. I hope this helped. All the best, Dr. Alma