7 Science-Backed Side Effects Of Drinking Too Much Water

All your life, you must have heard you need to drink plenty of water to avoid dehydration – 8 glasses, each of 8 oz, to be precise. But there is such a thing as water intoxication, caused by drinking too much water too frequently. Usually, in a healthy person, the kidneys can excrete around 6 gallons (about 22.7 L) of water a day,1 but only close to 1 L per hour. So drinking more than 1 L water per hour consistently can cause overhydration. The most common side effect is, of course, excessive urination, but there are other dangerous side effects. While healthy people may not show these side effects immediately, endurance athletes, people with kidney and heart problems, people on drugs like ecstasy, and infants with immature kidneys will have a lower threshold. Here’s a look at the side effects of drinking too much water.

1. Swells Up Your Cells

Your body has sodium and potassium ions that act as electrolytes in the body and maintain fluid balance between your cells and your blood. When there is excess water in the blood and a higher amount of salts and ions within the cells, water rushes into the cells, swelling them up. This is especially dangerous for neurons or nerve cells in the brain, where space is restricted by the skull. The result can be headaches, seizures, brain injury, coma, and even death.


2. Lowers Sodium Levels Abnormally (Hyponatremia)

Drinking too much water can also upset your body’s careful balance of sodium. This critical mineral should hover between 135 and 145 mEq/L. But when it drops below 135 mEq/L, a condition called hyponatremia develops. This too results in water from the blood stream flowing into the cells, making them swell.

Hyponametria is more likely in athletes who lose a lot of sodium through sweat. Drinking water in this condition only dilutes the sodium density further. Hyponatremia has been seen to even cause death in athletes.2


You’ll start to notice mild symptoms as sodium levels dip below 120 mmol/liter. Typically, symptoms like confusion or muscle cramps will be more visible under 110 mmol/liter. But when levels drop to 90 to 105 mmol/liter, your symptoms will probably become more severe. At first, you might feel drowsy, but it may result in a coma. Now, if you’ve had a lot of water in a very short time, the progression from mild to severe may happen pretty fast.3

3. Lowers Potassium Levels Abnormally (Hypokalemia)

Overhydration can also lower potassium levels in the body. Loss of potassium may cause hypokalemia, the symptoms of which are vomiting, low blood pressure, paralysis, nausea, and diarrhea.


This effect may be even more pronounced if you are on anti-diuretic medicines like vasopressin.4 The medicine is the synthetic form of the hormone vasopressin, which helps retain water in the body, especially in times of stress such as physical exertion. So if your body is already on a water-retention mode and you keep drinking more water, the result is disastrous.

4. Causes Muscle Cramps

As mentioned before, consuming too much water will lead to a drop in your body’s electrolyte levels. The resulting fluid imbalance also affects your muscular function and could lead to muscle spasms and cramping. If you’re involved in high-endurance activities, it’s important to not only drink more water but also to replenish your electrolytes with sports drinks.


5. Overwhelms The Kidneys

As you know, kidneys help filter toxins from blood. The first stage of filtration happens in a cluster of capillaries at the end of each nephron (the basic functional unit of kidneys). The toxins are then flushed out with urine.

Overhydration can affect the glomeruli because your kidneys need to work overtime to filter the extra water from your blood. So when you drink liters of water within an hour, your kidneys get overwhelmed. Drinking up to 800 to 1000 ml of water in an hour should be fine if you’re in otherwise normal health.


Overhydration is particularly dangerous when you have kidney problems. Researchers suggest that it can actually cause chronic kidney disease progression. It may also spark an increased risk of developing cardiovascular disease.5

6. Strains The Heart

Your body has an effective water absorption mechanism. Almost 80% of the fluids you drink is absorbed by the small intestine through a process called osmosis. Water then enters the blood stream, thereby increasing the overall volume of your blood. Drinking too much water can put undue strain on your heart due to the increase in blood volume and also lead to seizures in some cases.


Kidney function and heart health are also closely related. Patients with congestive heart failures or other heart issues that also affect the kidneys tend to retain more water in the body, compounding the problem. In their case, drinking too much water can stretch the heart muscle fibers and result in heart failure.6

7. Makes You Feel Tired

Excretion of fluids is mainly the function of your kidneys. When you drink more water than is needed by your body, it’s your kidneys that are strained the most. They need to work hard to remove excess water, which can lead to a stress reaction from your hormones. This could make you feel tired or fatigued. Moreover, the dilution of electrolytes could trigger exhaustion.


Drinking Chlorinated Water For A Long Time Can Cause Cancer

As much as we would to think that tap water is safe to drink, the fact remains that most drinking water in the United States is treated with chlorine to disinfect it. Drinking too much of chlorinated water over a period of time means increased intake of chlorine. Studies have shown that the risk of bladder cancer increased with intake of tap water and beverages made with tap water.7

How Much Water Should You Drink?

But how much you need to drink really depends on your age, gender, body weight, activity levels, metabolism, and medication as well as environmental conditions.8 9 People in temperate climates and with little physical activity may not need the 8 glasses of water daily. The National Health Services, UK, recommends limiting intake to 6 to 8 glasses of water, totaling about 1.2 liters a day,10 especially when you drink other fluids and water-filled foods.

The general rule to follow is to watch out for your body’s thirst signals. In a healthy person, the color of the urine is a good indicator as is the number of times you pee in a day. On hot and humid days and on days that you do strenuous exercise, drink 1.5 to 2.5 cups more, preferably with some electrolytes to balance the salts. But make sure you drink the water in small quantities through the day and not at one go.