Drinking too much water can lead to a condition called hyponatremia, which is when the sodium levels in your blood become abnormally low. This electrolyte imbalance can sometimes cause a low heart rate. In most cases, drinking too much water alone will not drastically lower heart rate, but it can contribute to an already existing heart arrhythmia or be dangerous for certain populations.
What is hyponatremia?
Hyponatremia specifically refers to low blood sodium concentrations in the body. This occurs when there is an excess of water in proportion to the amount of sodium. Sodium is an electrolyte that helps regulate the amount of water that’s in and around your cells. When sodium levels get too low, water starts to move into the cell, causing them to swell. This swelling can impair cell functioning and cause severe symptoms.
Some major causes of hyponatremia include:
- Drinking too much water
- Kidney disorders
- Liver disease
- Congestive heart failure
- Syndrome of inappropriate antidiuretic hormone (SIADH)
Athletes and people who drink excessive amounts of water are typically at the greatest risk of developing hyponatremia. Your kidneys are only able to excrete about 1 liter of water per hour, so if you’re drinking more than that, the excess water can begin to dilute the sodium in your blood.
Signs and symptoms
Mild hyponatremia may have no signs or symptoms. But as blood sodium levels get lower, the following may develop:
- Headache
- Nausea and vomiting
- Muscle weakness, spasms or cramps
- Seizures
- Confusion
- Drowsiness
In severe cases, excessively low sodium can also lead to coma and death. Even mild hyponatremia often requires medical attention, as sodium imbalance can rapidly worsen.
How can hyponatremia cause low heart rate?
There are a few reasons why the electrolyte imbalance of hyponatremia can potentially lower heart rate:
- The body attempts to compensate for cellular swelling and fluid shifts by suppressing adrenal hormones like aldosterone. This alters sodium and fluid levels throughout the body, including the heart.
- Excess water accumulates in the ventricular chambers of the heart, stretching the muscle fibers. This makes it more difficult for electrical signals to spread through the heart and can disrupt the heart’s normal beating rhythm.
- Fluid shifts into the pericardial sac surrounding the heart, called pericardial effusion. This added fluid can put pressure on the heart and affect its ability to pump normally.
These changes to the heart’s normal rhythm are called arrhythmias. In hyponatremia, arrhythmias often take the form of bradycardia, which is a slower than normal heart rate (less than 60 beats per minute). The heart may also beat irregularly or even stop for short periods of time.
Who’s at risk?
For most healthy individuals, accidentally consuming too much water is unlikely to drastically affect heart rate or rhythm. Endurance athletes and people who drink extreme amounts of water are at the greatest risk.
However, certain populations may be more vulnerable to the effects of mild hyponatremia on heart function:
- Infants and young children – Their smaller body size and fluid requirements mean sodium can become diluted more quickly.
- Older adults – Aging kidneys have a decreased ability to conserve sodium and excrete excess water.
- People with heart failure – They already tend to have a low blood sodium level and are sensitive to fluid shifts.
- People taking certain medications – Including diuretics, antidepressants and anti-seizure drugs.
So even mild hyponatremia can potentially trigger arrhythmias and low heart rate in those who already have underlying heart issues.
How much water is too much?
There are no definitive guidelines on exactly how much water is considered excessive and potentially dangerous. The appropriate amount of water intake varies substantially between individuals based on age, environment, activity level, diet and health status.
However, most experts agree healthy adults should not need to drink more than 0.5-1.0 liter (17-34 ounces) of water per hour at most. Consuming multiple liters within a short time frame will likely result in excretion of excess water through urine. But factors like medications, exercise and health conditions can decrease urine output and increase risk of overhydration.
Drinking more than 1-2 liters per hour for several hours can dilute blood sodium levels and potentially lead to hyponatremia in vulnerable people. Endurance athletes are especially susceptible because high sweat losses increase daily fluid needs. Cases of fatal hyponatremia have occurred when athletes consume as much as 3-4 liters per hour during prolonged exercise.
Treatment
Treatment of hyponatremia focuses on raising sodium levels back to normal through:
- Fluid restriction – Preventing further water intake until sodium returns to balance.
- Hypertonic saline – Getting sodium directly into the bloodstream via an IV solution.
- Treating underlying causes – Like improving kidney function or altering medications that may contribute.
Mild, symptomatic hyponatremia can often be treated with just fluid restriction until urine output increases. More severe cases may require hospitalization for close monitoring of fluid balance and intravenous saline solutions to rapidly correct sodium levels.
Once sodium is restored, symptoms like fatigue, nausea and headache typically resolve. Even if the heart rate has been slowed from hyponatremia, normal rhythm usually resumes as well. However, left untreated, the electrolyte imbalance and fluid shifts can have serious and even fatal consequences.
Can you drink too much water on keto?
The ketogenic diet involves following a very low carbohydrate, high fat meal plan. This forces your body into a metabolic state called ketosis, where it burns fat for fuel.
There is some evidence that people following a keto diet may be at greater risk for hyponatremia and low sodium levels when drinking excessive amounts of water.
This seems to occur partially because carb restriction enhances urine excretion of sodium and fluids. Reasons why keto may increase hyponatremia risk include:
- Reduced insulin levels enhance sodium lost in urine.
- Ketones themselves can act as a diuretic and increase water excretion.
- Low carbohydrate intake reduces fluid retention in muscle.
- More water is excreted when metabolizing fat versus carbs.
One study found blood sodium dropped significantly lower during 3 hours of rehydration in athletes on keto compared to those eating a high carb diet. Their urine sodium losses were also greater.
Research overall indicates people following a ketogenic diet may be prone to increased water and sodium excretion through urine. It’s important to adequately replace electrolytes and avoid overhydrating while on keto.
Tips for staying hydrated on keto
Here are some tips for staying properly hydrated and avoiding hyponatremia on keto:
- Moderate total water intake based on thirst and urine color. Urine should be a pale yellow, not completely clear.
- Focus on getting fluids from food sources like broths, soups and high water content vegetables.
- Supplement with electrolytes like sodium, potassium and magnesium.
- Avoid excessive plain water intake, particularly before or during exercise.
- Monitor hydration with urine specific gravity or urine electrolyte measurements.
- Increase salt intake to compensate for greater urinary losses.
Being in ketosis itself does not directly cause low heart rate. But depleting electrolytes and overhydrating to a dangerous degree can potentially affect heart rhythm in some individuals.
Can dehydration cause low heart rate?
Being dehydrated causes changes in blood volume and composition that can also impact heart rate and rhythm. When the body loses more water than is taken in, blood plasma volume is reduced. This leads to:
- Concentrated levels of electrolytes like sodium and potassium.
- Less fluid for the heart to pump through blood vessels.
- Increased blood viscosity.
These factors may provoke the heart to beat slower to compensate for reduced circulating volume. The heart doesn’t need to work as hard when less blood is making its way through the arteries and veins.
Some small studies have found average heart rate decreases by up to 10 beats per minute in healthy people deprived of fluids over 24-36 hours. However, severe dehydration can also sometimes produce tachycardia instead, likely due to the elevated catecholamine response it triggers.
Overall, research indicates mild to moderate dehydration tends to lower heart rate, while severe dehydration with major electrolyte disturbances can cause unpredictable cardiac arrhythmias. Getting sufficient fluids and electrolytes can help maintain normal heart rhythm.
Can drinking too much water flush out electrolytes?
Electrolytes are minerals that help conduct electrical signals in the body and perform other essential functions. The main electrolytes in your blood, tissues and organs include:
- Sodium
- Potassium
- Chloride
- Calcium
- Magnesium
- Phosphate
These electrolytes need to be maintained in proper balance for normal nerve, muscle and heart activity.
Does excessive water consumption affect electrolyte levels? Research shows drinking large volumes can lead to excessive urinary losses of certain electrolytes like sodium, potassium and chloride.
This occurs because the kidneys are unable to reabsorb and conserve normal proportions of electrolytes when processing huge amounts of water. Electrolytes get washed out because the kidneys essentially become overwhelmed.
For example, studies show plasma potassium levels begin dropping within 1-2 hours if athletes drink 1-2 liters per hour during long endurance exercise. Just 1 hour of rehydrating with 1.5 liters of water also markedly increases sodium excretion in healthy adults.
Most evidence indicates that consuming water beyond normal hydration needs can essentially flush out sodium, potassium and chloride through the urine. However, drinking excess water alone does not appear to have significant effects on other key electrolytes like calcium or magnesium in healthy people.
Table showing effects of overhydration on urinary electrolyte excretion
| Electrolyte | Change with Overhydration |
|---|---|
| Sodium | Markedly increased urinary excretion |
| Potassium | Moderately increased urinary excretion |
| Chloride | Markedly increased urinary excretion |
| Calcium | No significant change |
| Magnesium | No significant change |
Can drinking too much water stop your heart?
In very rare instances, consuming excessive amounts of plain water can provoke cardiac arrest in susceptible individuals.
Documented cases of death directly from overhydration without another underlying condition are extremely unusual. But there have been occasional reports of fatal hyponatremia in endurance athletes who drank more than 10-15 liters within a short time frame.
Exactly how overhydration can potentially stop the heart is not fully understood. It likely involves a combination of:
- Profoundly low sodium levels below 120 mmol/L.
- Disruption of heart electrical activity and conduction from electrolyte shifts.
- Fluid changes increasing pressure around the heart.
- Cell swelling triggering ventricular arrhythmias.
The cardiac arrest these mechanisms can provoke are most likely to occur in scenarios of extreme overhydration. Consuming 3-6 liters or more per hour for multiple hours seems to be the threshold where water intoxication risk becomes significant.
But even lower levels of excessive fluid intake can potentially worsen underlying heart conditions. Hyponatremia from overhydration is most dangerous in those with pre-existing cardiac issues like heart failure or arrhythmias.
Can you drink too much water on keto?
The ketogenic diet involves following a very low carbohydrate, high fat meal plan. This forces your body into a metabolic state called ketosis, where it burns fat for fuel.
There is some evidence that people following a keto diet may be at greater risk for hyponatremia and low sodium levels when drinking excessive amounts of water.
This seems to occur partially because carb restriction enhances urine excretion of sodium and fluids. Reasons why keto may increase hyponatremia risk include:
- Reduced insulin levels enhance sodium lost in urine.
- Ketones themselves can act as a diuretic and increase water excretion.
- Low carbohydrate intake reduces fluid retention in muscle.
- More water is excreted when metabolizing fat versus carbs.
One study found blood sodium dropped significantly lower during 3 hours of rehydration in athletes on keto compared to those eating a high carb diet. Their urine sodium losses were also greater.
Research overall indicates people following a ketogenic diet may be prone to increased water and sodium excretion through urine. It’s important to adequately replace electrolytes and avoid overhydrating while on keto.
Tips for staying hydrated on keto
Here are some tips for staying properly hydrated and avoiding hyponatremia on keto:
- Moderate total water intake based on thirst and urine color. Urine should be a pale yellow, not completely clear.
- Focus on getting fluids from food sources like broths, soups and high water content vegetables.
- Supplement with electrolytes like sodium, potassium and magnesium.
- Avoid excessive plain water intake, particularly before or during exercise.
- Monitor hydration with urine specific gravity or urine electrolyte measurements.
- Increase salt intake to compensate for greater urinary losses.
Being in ketosis itself does not directly cause low heart rate. But depleting electrolytes and overhydrating to a dangerous degree can potentially affect heart rhythm in some individuals.
Conclusion
Drinking too much water can dilute blood sodium levels and lead to hyponatremia in those who over-hydrate. This electrolyte imbalance can contribute to an abnormally low heart rate in some cases. Groups like athletes, infants, and older adults appear to be at highest risk.
Consuming well over 1-2 liters per hour consistently seems necessary to lower heart rate substantially. The effects are usually transient and unlikely to be life-threatening in healthy people. But those with underlying cardiac conditions can experience severe arrhythmias and require prompt treatment.
Maintaining adequate electrolyte intake, monitoring hydration status, and avoiding excessive plain water intake can help prevent hyponatremia and associated heart rhythm issues. Being on a ketogenic diet may increase susceptibility to overhydration through increased urinary water and sodium losses.