Too much and not enough

Not getting enough?

A whole range of body processes work to keep your fluid levels relatively stable - the thirst mechanism and kidney function are just two. Generally, your total body fluid levels vary by less than one percent, regardless of fluctuations in what you drink. But there are dangers if you persistently drink too little.

It takes only small changes in your overall fluid levels to destabilise your system and bring about the symptoms of dehydration - as little as one to two percent of your body weight can do it. If you were 20 percent dehydrated or more, you'd die.

Early signs of dehydration include headache, fatigue, loss of appetite, flushed skin, heat intolerance, light-headedness, dry mouth and eyes, a burning sensation in the stomach and dark urine with a strong odour.

If dehydration becomes more advanced, you may get symptoms such as difficulty swallowing, clumsiness, shrivelled skin, sunken eyes and dim vision, painful urination, numb skin, muscle spasms and delirium.

Of course, long before these things start happening a powerful thirst should kick in. Your kidneys are also super-efficient at regulating water - if things get desperate, you'll probably stop urinating.

If you're not sure whether you're getting enough water, a simple check is to keep an eye on the colour of your urine. It will be yellow first thing in the morning, but should become paler by mid-morning. If it doesn't, you're not drinking enough.

Don't wait till you get thirsty to drink. Thirst is actually an emergency response. You don't become thirsty until you're already dehydrated. The typical symptoms, such as a horrible taste, dry throat and cravings for cool wet liquid, are physiological responses your body uses to signal its dehydration.

Too much water

It's possible to drink too much water. Your body's fluid balance can be dangerously upset if you drink more water than your kidneys can excrete. Your body cells swell, and you may feel drowsy and weak and suffer convulsions.

You'd need to drink more than six litres over a short period for this to be a danger, and you'd probably make yourself sick in the process. But it does happen. Several people have died from drinking too much water after taking the recreational drug ecstasy.