Hi...., Dehydration can be mild, moderate or severe, depending on how much of your body weight is lost through fluids. Two early signs of dehydration are thirst and dark-coloured urine.... Other symptoms may include: dizziness or light-headedness, headache,  tiredness, dry mouth, lips and eyes.. If dehydration is ongoing, it can affect your kidney function and increase the risk of kidney stones. It can also lead to muscle damage and constipation...