The question: I'm a woman in my 30s and I find that I am really thirsty all the time. I try to watch my salt intake, so I don't think that's it. In a given day, though, I can drink anywhere from three to four litres of water. Is this too much? My blood pressure is also on the low end of normal. Could the two be related?
The answer: Under normal circumstances, consuming too much water to the point of danger is exceptionally rare. To test the waters (so to speak) I brought this question up to my emergency room colleagues to hear if they had treated people for drinking too much water. While they confirm it's a rare occurrence, they had all treated people for excess water consumption. Often, these situations happen with athletes after heavy exercise, or in the hot summer months when people who had been sitting in the sun have good intentions of rehydrating – they all drank too much water too fast.
While water is a necessary part of our health, just like anything in life, too much of a good thing can be dangerous. While it is very rare to become "water intoxicated" – it is possible to overwhelm your body by drinking too much, too fast. Generally, your body can adjust to water by activating the kidneys to get rid of the excess through urination. But when the kidneys can't keep up, it can lead to a dilution and drop of important electrolytes (salts) in the body, known as hyponatremia. As your body attempts to restore the balance, you may experience nausea, vomiting, fatigue or muscle cramps. In more extremely rare but serious cases, it can result in potentially fatal swelling of the brain.
In your case, if you are spreading your water consumption out throughout the day in a gradual manner, your body is likely able to accommodate the excess fluid and create balance as needed without negative effect. Our individual water needs vary based on our baseline health, medical conditions, age, external temperature and if we've been active or exercising. The popular idea of eight glasses of water a day is a bit of a myth and is not specific enough for each individual's actual needs. It also does not take into account that all fluids, including the water in our food, teas, and coffees, should be included in your total daily intake.
My larger concern is that you're constantly thirsty. Thirst is stimulated by dehydration, excess salt in your diet and certain medications like those used to treat allergies, blood pressure and mental-health conditions (including common antidepressants and some antipsychotics). Blood pressure does go down when you're dehydrated, so if you're on the low end of normal, the two may be certainly be related and may be contributing to your thirst and stimulation to drink more water.
It's important to hydrate well, but it does sound like you are potentially drinking too much, so it's important to get to the bottom of why this is happening. See your doctor to rule out more serious causes of chronic thirst like diabetes, which can be screened with some simple blood tests.
Dr. Sheila Wijayasinghe is the Medical Director at the Immigrant Womens' Health Center, works as a Staff Physician at St. Michael's Hospital in their Family Practice Unit and at Hassle Free Clinic, and established and runs an onsite clinic at Women's Habitat Shelter in Etobicoke. She has a special interest in womens' health, health promotion, and care of marginalized populations.
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