What happens when you drink too much water: Know the health risks

Water is essential for life, powering everything from digestion and circulation to temperature control and brain function. Yet, while dehydration is widely discussed, overhydration is a lesser-known but potentially dangerous condition. Drinking excessive water, especially in a short period, can dilute vital electrolytes like sodium and disrupt the body’s fluid balance. This can lead to water toxicity, medically known as hyponatraemia , where cells swell due to a sodium imbalance, placing dangerous pressure on the brain. Overhydration is not common, but it can become serious in athletes, people with certain medical conditions, or those who force high water intake without listening to thirst cues. While the “eight glasses a day” rule offers a rough guide, hydration needs vary based on age, activity, climate, and health. Understanding the signs, risks, and safe limits can help prevent complications.


Drinking too much water is not always healthy

According to a study published in The New England Journal of Medicine, drinking excessive water can dangerously dilute sodium levels in the blood, leading to hyponatraemia, a condition that disrupts fluid balance, nerve activity, and muscle function. When sodium levels fall below 135 mEq/L, water moves into cells, causing them to swell. The brain is particularly vulnerable since the skull cannot expand to relieve pressure. Research shows early symptoms may include fatigue and poor concentration, while severe cases can escalate to confusion, seizures, respiratory distress, coma, and even death. The study also highlights that water intoxication, although rare, has been reported in endurance athletes, extreme water-drinking incidents, and in individuals using recreational drugs such as MDMA, which increase both thirst and fluid retention. Risk further rises when the kidneys are unable to excrete excess water efficiently, overwhelming the body’s natural electrolyte balance.



Health risks of drinking too much water



Persistently clear urine

One of the earliest and most noticeable effects of drinking too much water is clear, colourless urine. While light yellow urine indicates good hydration, consistently clear urine often means the body is getting more water than it needs, diluting essential electrolytes in the process. This can be an early warning sign of overhydration, especially when paired with frequent drinking and a lack of physical activity or heat exposure to justify high fluid intake.



Frequent urination

Urinating more than 8 to 10 times a day may signal that the kidneys are working overtime to remove excess water. Although bathroom frequency can increase with caffeine or high fluid intake, a consistent need to urinate, especially when urine is clear, can indicate that the body is unable to maintain a healthy water-sodium balance. This constant flushing can also strip the body of electrolytes over time.



Nausea, vomiting and dizziness

As sodium levels fall due to excess water, the body begins to react adversely. Nausea, occasional vomiting, and dizziness can occur when an electrolyte imbalance interferes with digestive and neurological function. These symptoms are often mistaken for dehydration, but in overhydration, they stem from fluid overload rather than a lack of fluids.



Headaches from brain swelling

Throbbing, persistent headaches are a key sign of overhydration. When sodium levels drop dangerously low, water enters brain cells, causing them to swell, a condition known as cerebral oedema. Since the skull cannot expand, even slight swelling increases pressure, triggering intense headaches that may worsen over time and don’t improve with drinking more water.



Brain fog, confusion and irritability

Excess water can impair normal brain function. When neural cells swell, people may feel mentally slow, confused, forgetful, or unable to focus. Disorientation, sudden mood changes, irritability, or brain fog are all neurological signs that the brain is under pressure due to a water volume imbalance rather than dehydration.



Visible swelling and skin discolouration

Fluid overload can make parts of the body appear puffy, especially the hands, feet, lips, and face. This swelling happens because excess water enters cells and tissues faster than the kidneys can remove it. The skin may also look pale, stretched, or slightly discoloured because of fluid accumulation under the surface.



Fatigue and physical exhaustion

Drinking too much water forces the kidneys to work harder than normal to filter and flush the excess fluid. This strain can trigger hormonal stress responses in the body, leaving a person feeling unusually tired, weak, or physically drained. Some people report difficulty getting out of bed or feeling wiped out despite resting, as the body struggles to maintain internal balance.



Muscle cramps and spasms

Electrolytes like sodium, potassium, and magnesium help regulate muscle function. When water dilutes these electrolytes, muscles may cramp, twitch, or spasm without warning. These cramps can affect the legs, arms, or abdomen and may feel similar to exercise-induced muscle fatigue, even if no strenuous activity occurred.



Seizures and loss of consciousness

In severe cases of overhydration, sodium levels can drop so drastically that the brain’s electrical signalling becomes disrupted. This can trigger seizures, fainting, or sudden loss of consciousness. These symptoms indicate a medical emergency requiring immediate attention, as the brain is struggling to function under pressure.



Breathing difficulty and respiratory distress

In extreme water toxicity, brain swelling can affect areas that regulate breathing. As pressure increases, normal respiratory function can slow or become irregular, leading to shortness of breath or difficulty breathing. Without prompt medical care, this can quickly become life-threatening.



Safe water intake and prevention of water toxicity

According to the Institute of Medicine (IOM), daily hydration needs vary based on climate, age, body size, activity levels, and overall health. The report recommends 2.7 litres per day for adult women and 3.7 litres for adult men, including fluids from food sources as well as drinks. It also emphasises that hydration should ideally be guided by natural thirst cues rather than forced excessive intake.
Research further notes that fluid needs increase for active individuals or hot environments, where plain water alone may not be enough and electrolyte balance becomes essential, particularly for athletes. The IOM also highlights that infants under six months should not be given extra water beyond breast milk or formula, as their kidneys are not mature enough to manage additional fluid, increasing the risk of water intoxication.


Disclaimer: This article is for general informational purposes only and is not a substitute for professional medical advice, diagnosis, or treatment. Always seek the guidance of a qualified healthcare provider regarding any medical condition or lifestyle change.