What Is Hypernatremia?

Medically Reviewed by Murtaza Cassoobhoy, MD on May 29, 2023
5 min read

Hypernatremia is the medical term to describe too much sodium in your blood. Sodium is one of the body's electrolytes — found mostly in your blood — that is important for many bodily functions. However, when there's too much, it is an imbalance in your body's electrolytes and can cause serious problems.   

Sodium helps to regulate your blood volume, your blood pressure, the pH of your body, and the electrical conductivity of your cells. This means that sodium not only helps balance the amount of water that is on the inside or outside of your cells, but it's also critical for how your muscles and nerves work. Your kidneys help regulate how much sodium is in your body — most of it is removed through urine, and a small amount comes out in sweat.

Hypernatremia occurs when the balance of water and sodium in your blood is off: there's either too much sodium or not enough water. This can happen when too much water is lost or too much sodium is gained (or accumulated) in the body. Doctors define hypernatremia as a measurement of over 145 milliequivalents per liter — a normal level is considered between 136-145 milliequivalents per liter.

In healthy people, the brain automatically balances the amount of water and sodium in your body by controlling intake and output — getting thirsty or urinating. If your brain detects that your body has elevated sodium levels, it can regulate the amount by increasing how much is removed from your bloodstream by your kidneys and can also make you drink water by making you feel thirsty.  

Hypernatremia is usually a symptom of dehydration. Most cases of hypernatremia are mild and easily corrected by fixing dehydration. Usually, when a person starts to get dehydrated and feel thirsty, they are sensing a mild case of hypernatremia and reversing it by drinking water or an electrolyte-containing sports drink. However, more moderate cases can require medical care.

Symptoms of hypernatremia include: 

  • Muscle weakness
  • Restlessness
  • Extreme thirst
  • Confusion
  • Lethargy
  • Irritability
  • Seizures
  • Unconsciousness

Hypernatremia can be very serious, especially in small children. It can be caused by dehydration due to diarrhea, vomiting, excessive sweating, significant burns, or other systemic problems. 

Similarly, hypernatremia can cause very serious problems in the elderly. Sometimes as the brain ages, it does not pick up on electrolyte imbalances as quickly, leading to too much sodium in your blood. Older people can also have kidney problems that can contribute to hypernatremia. 

A doctor can diagnose hypernatremia through a blood test. Sometimes, urine tests can be used as well.

The treatment for hypernatremia is to get the balance of fluid and sodium in your body back to the ideal level. If your hypernatremia is more than mild, your doctor will likely replace the fluids in your body using an IV. This will supply fluids directly into your bloodstream, balancing the amount of sodium that is in your blood.

In most cases, hypernatremia is fixable. However, your doctor will want to determine the underlying cause of your hypernatremia to make sure there aren't other problems in your brain or kidneys that need to be treated.

One of the most severe complications of hypernatremia is a ruptured blood vessel in your brain. Called a subarachnoid or subdural hemorrhage, this kind of bleeding in your brain can cause permanent brain damage or death.

If doctors are able to detect and begin treating hypernatremia before it gets too severe, restoring the balance of sodium and fluids in your body, they can prevent serious complications like brain damage, seizure, or death.

Seventy percent to 80% of the sodium in U.S. diets comes not from the salt shaker but from packaged, processed, restaurant, and store-bought foods. Only about 5% comes from salt added during cooking; about 6% comes from salt added at the table.

The Center for Science in the Public Interest released a report that found 85 out of 102 restaurant meals from 17 popular chains had more than a full day's worth of sodium. Some had more than 4 days’ worth.

But reducing sodium is not easy. Our taste buds have grown accustomed to the salty taste of most foods, and unlike for sugar, there are few convincing substitutes. Not only does sodium flavor foods, but it also acts as a preservative and as an inhibitor in leavening agents. Sodium is found not only in salt but also in baking soda, baking powder, and MSG.

In the last several years, scientists have begun to investigate whether salt affects obesity. Here’s what they have found:

  • In 2015, British and Chinese researchers reported that body fat increased for children and adults on high-salt diets. Eating an extra gram of salt each day increased the risk of obesity in children by 28% and in adults by 26%. The study authors said they don’t know why salt has this effect, but other studies suggest that it may change the way our bodies burn fat.
  • An Australian study published last year linked high-salt diets with a 23% increased chance of obesity in schoolchildren. Those children may eat more because the salt makes the food taste good, the authors suggest. They also speculate that when they get thirsty after a salty meal, the children reach for easily available high-calorie sodas.
  • Another Australian study from 2016 tied salt to an 11% rise in the amount of food and calories that adults take in. The authors say salt improves the flavor and that likely tempts people to eat more.

While these studies show a link between salt and body fat, increased eating, and obesity, they don’t show that salt makes any of those things happen. More research needs to be done to fully understand salt’s role.

Still, if you're one of the 2 out of 3 adults at risk for health problems from too much sodium, the CDC report should serve as a wake-up call to lower the amount of sodium you consume.

The easiest way to prevent hypernatremia is to ensure that you are well hydrated and consuming a reasonable amount of sodium. 

The average adult should drink between 4 to 6 cups of water each day. If you are on certain medications, very active, in a hot climate, or at an elevated altitude, you should drink more to avoid dehydration and hypernatremia.

The American Heart Association recommends an ideal limit of 1,500 milligrams per day of sodium for a healthy adult. The organization notes that the average intake for an American is more than 3,400 milligrams per day — an amount that can contribute to imbalances like hypernatremia, among other serious health problems. The AHA recommends swapping prepackaged and restaurant food for homemade versions and keeping an eye on your sodium intake.

A healthy, balanced diet and proper hydration should help most people avoid hypernatremia. However, hypernatremia can be the result of an electrolyte imbalance caused by other conditions. In this case, it is a medical emergency and is manageable by doctors.