Can Drinking Too Much Water Make You Dizzy?
Water intoxication can lead to dangerous drops in sodium and related symptoms
Medically reviewed by Brigid Dwyer, MD
Drinking too much water can cause dizziness, confusion, and nausea when your intake exceeds what your kidneys can eliminate through urination. On rare occasions, severe fluid overload, or water intoxication, can even be fatal.
Too much water dilutes the amount of sodium in the blood needed for the body to function normally. Low sodium levels, known as hyponatremia, can affect many organ systems, most predominately the central nervous system.
Drinking too much water is rarely a problem for healthy people, but you don't have to have an underlying kidney condition for this to affect you.
This article explains how drinking too much water can lead to dizziness and other symptoms, as well as serious complications.
What Is Water Intoxication?
Water intoxication, also known as water poisoning, occurs when drinking too much water causes an imbalance in electrolytes. Electrolytes are minerals in your body that have an electric charge and affect how your body functions.
Sodium is one of the most important electrolytes. This mineral has a number of vital functions in the body, including:
Enabling nerve impulses between nerve cells
Contracting and relaxing muscles
Maintaining a proper balance of water and minerals in the body
A healthy adult needs around 500 milligrams (mg) of sodium per day to maintain these vital functions. When you drink too much water, you not only reduce the ratio of water to sodium but also promote urination, which can clear sodium from the body.
Depending on your levels, you may develop:
Hyponatremia: Sodium concentrations below 135 moles per liter (mmol/L)
Severe hyponatremia: Sodium concentrations below 125 mmol/L
How Much Water Leads to Water Poisoning?
In order for water intoxication to occur, you need to drink more water than you can excrete in urine. In healthy adults, the kidneys can excrete about a liter of water per hour.
With that said, the amount may be far lower if you have kidney disease or other medical conditions that affect urine output.
A 2021 study in BMJ Open suggests that the median intake of water needed for water intoxication is 5.3 liters (1.4 gallons) over four hours. This is an average and not an accurate threshold for everyone.
There is no set level at which a person might experience water intoxication. This can vary by a person's body size, weight, physical status, and underlying medical conditions.
Dizziness and Other Symptoms of Water Intoxication
Water intoxication often causes no symptoms. It is only when hyponatremia is severe that a person might experience notable and sometimes serious symptoms.
Mild symptoms of hyponatremia include:
Headaches
Nausea
Fatigue
Lethargy
Weakness
Loss of appetite
Poor balance and unsteadiness
Difficulty thinking or concentrating
Muscle cramps
When sodium levels drop below 110 mmol/L, water will start to enter brain cells and causes them to swell, leading to cerebral edema (fluid overload of the brain). This can lead to more serious symptoms, such as:
Dizziness and fainting
Vomiting
Confusion
Changes in vision
Neck stiffness and pain
Seizures
Coma
Hyponatremia can be very difficult to manage because it progresses so rapidly and the resulting damage can be severe. Also, it is important to reverse hyponatremia slowly, as overcorrecting can lead to neurological problems.
Causes of Water Intoxication
Hyponatremia, the main consequence of water intoxication, can occur when you drink an excessive amount of water and either have normal or low concentrations of sodium in your blood.
On the other hand, you might also have high-volume hyponatremia. This is when both your water and sodium levels are high but an underlying medical condition like kidney disease, liver cirrhosis, or heart failure impedes the normal excretion of water in urine.
There are several situations that can contribute to the onset of water intoxication and hyponatremia, including weight loss, excessive sweating and fluid replenishment, and diabetes.
Weight Loss
People will sometimes drink excessive amounts of water to lose weight. While water can certainly aid with weight loss by increasing a feeling of fullness, you don't want to overdo it.
The ideal amount of water for the average person is between 9 to 12 cups per day, depending on activity levels. Drinking anything more than this will unlikely increase weight loss.
As a general rule, thirst is a reliable indicator of the body’s water needs.
Performance Sports
It is normal for athletes to drink fluids to cool off and replenish water lost through sweat. However, when there is extreme physical exertion, thirst may not be the best guide.
Hyponatremia is common among marathon and triathlon participants due to excessive water intake and extreme sodium loss through sweating.
As such, performance athletes should obtain professional guidance to ensure enough water is consumed to avoid dehydration but not so much that water poisoning can occur.
Diabetes
Hyponatremia can occur in people with diabetes due to increased thirst (a common symptom of the disease). Uncontrolled high blood sugar also contributes to frequent urination which can rid the body of electrolytes.
If your water intake exceeds the excretion of sodium and other electrolytes, hyponatremia can occur.
The best way to avoid this is by managing your diabetes with diet, routine exercise, and diabetes medications. By bringing your blood sugar under control, you'll be less likely to experience excessive thirst and urination.
