We all know water is good for us: in fact, it makes up 60% of our bodies. So is it really possible to drink too much water? How much is too much and how do we know?
There is a golden rule that we should all be drinking at least 8 glasses a day, but this varies from person to person. The right amount of water can change with your age, fitness and activity levels, medications, and weather.
Our hydration levels are managed by our blood pressure and kidneys. As long as the kidneys are in a fit and healthy state they can excrete up to 1 liter of excess water per hour, so if you drink too much, too fast your kidneys won’t be able to keep up.
As water builds up in the bloodstream your blood becomes diluted, and the water follows osmotic pressure into your cells. Osmosis describes the movement of water particles from an area with a low concentration of solutes, like freshwater or dilute blood, into an area with a high concentration of solutes, like saltwater or our stuff-filled cells. This osmotic pressure is why electrolytes are such an important part of hydration: sodium, potassium and other ions keep water in your bloodstream and buffer against de- and overhydration.
As water builds up in your cells and body cavities, cells burst and pressure builds up in your brain. Symptoms include nausea, fatigue and confusion.
Other warning signs of overhydration you should look for are interrupted sleep from frequent bathroom trips and completely clear urine.
The best way to stay hydrated and avoid overhydration is to listen to your thirst: your body will tell you when to drink.
- Always drink when you are thirsty
- Don't try to get ahead of your thirst
- Ensure you are getting enough electrolytes
Try to take regular small amounts during the day and aim for 2 to 2 ½ liters for an average healthy adult.
If you do feel you are overhydrated, cut back on the fluids immediately and consider taking electrolytes to replace your sodium levels or diuretics to flush the electrolytes and water into your urine. Remember that certain medications can affect your water levels, so ask your doctor whether overhydration is a risk when you’re prescribed a new medication.
Overhydration is quite common with long-distance runners and other endurance athletes but fairly uncommon for an average healthy person. However, it's good to know the warning signs and remember: listen to your thirst.
