Key takeaways:
A high sodium level in your blood is usually caused by not having enough water in your body, rather than too much sodium.
This can happen when you’re dehydrated and not drinking enough water. Other medical conditions can also affect your sodium level.
In most cases, the symptoms of a high sodium level are mild and easy to treat. But severely high sodium can lead to serious complications, like seizure or coma.
Sodium is one of the main electrolytes inside your body. Your sodium level is measured in the blood, but you can think of it as a way to check how much salt and water is in your body. When these levels get too high, it can affect more than just your fluid balance. Your brain can be quite sensitive to changes in sodium. So, we’ll review what causes high sodium, the symptoms to watch for, and how it’s treated.
What is hypernatremia (high sodium levels)?
Hypernatremia is the medical term for a high sodium level. A normal sodium level in the blood is 135 mEq/L to 145 mEq/L. Anything above 145 mEq/L is considered high. But as we’ll explain, the rate of change in sodium level can be just as important as the absolute number itself.
What causes a high sodium level?
A high sodium level is usually caused by severe dehydration. Instead of having too much sodium, it’s often caused by a loss of fluid that typically dilutes that sodium level. Common conditions that can lead to severe fluid loss include:
Sweating, especially from excessive heat or intense exercise
Vomiting or diarrhea
Increased urination, which can happen in people with diabetes or kidney disease
Medications like diuretics or laxatives
Infections or any illness that causes fever
On rare occasions, a high sodium level can happen if too much salt enters your body. This is hard to do just by eating salty foods. When this happens, it’s usually from getting intravenous (IV) fluids, which can have a lot of sodium.
What are the symptoms of a high sodium level?
The symptoms of a high sodium level depend on both the actual level and how quickly it rises.
The body doesn’t like fast changes in your sodium level. If the level changes slowly, your body has time to adjust. But rapid increases are more likely to cause more noticeable and serious symptoms.
Small or slow increases in sodium levels may cause symptoms such as:
Thirst
Muscle weakness
Restlessness
Nausea or vomiting
Poor appetite
When the sodium level climbs above 160 mEq/L, it can lead to more severe symptoms. But serious symptoms can also happen if the sodium level rapidly changes, like an increase from 135 mEq/L to 150 mEq/L.
These symptoms include:
Confusion
Lethargy
Seizures
Who’s most at risk of a high sodium level?
The body has built-in mechanisms to naturally prevent a high sodium level. When a sodium level starts to rise, your brain triggers the sensation of thirst. Most people respond by drinking water, which rehydrates the body before a high sodium level becomes a problem.
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There are some situations where that thirst mechanism doesn’t work properly, or someone can’t drink water when they need it. People at a higher risk of a high sodium level include those who:
Are older: As we get older, the thirst drive becomes weaker. Older adults often drink less water than younger adults, even when their body needs it.
Are exposed to excessive heat: This is especially true if you don’t have easy access to liquids.
Rely on caretaker help to hydrate: This would include children, older adults, or people with disabilities.
Have a condition that causes significant fluid losses: For example, someone with diabetes or gastroenteritis (the stomach flu) may be at higher risk.
Have a medical condition that causes an altered mental state: This could cause confusion or lethargy, which can affect thirst cues and your ability to interpret or act on those cues.
How do you diagnose a sodium imbalance?
Sodium levels are measured with a blood test. While there may be signs of a high sodium level, such as the symptoms we talked about above, the only way to know for sure is through a blood draw.
How do you treat a high sodium level?
The treatment for a high sodium level is rehydration. In mild cases, this might just mean drinking some extra water. In more severe cases, a person may need rehydration with IV fluids in the hospital.
Just like your body doesn’t like sodium levels to rise too quickly, it also doesn’t like them to drop (or return to normal) too quickly. This is especially true if the sodium level has been high for a long time. This means that treatment requires a special mix of water and electrolytes and close medical supervision. In more serious cases, healthcare professionals will check blood work frequently to make sure the sodium level isn’t dropping too quickly.
Because it’s important to reduce a high sodium level in a safe way, it’s always best to do this with the guidance of a healthcare professional.
How to prevent high sodium levels
The best way to prevent high sodium levels is to stay hydrated. This can be easier said than done, depending on what puts you at risk for dehydration or high sodium levels. But the following tips can help:
Make sure fluids are easily accessible. For many people, this may mean just keeping a glass or bottle of water within reach for when you get thirsty.
If you’re a caregiver for someone who may need help staying hydrated, try to make it easy for them. Use water bottles that are easy to see and hold, offer fluids they like to drink, and give gentle reminders to keep sipping.
If you’ve been vomiting or feel nauseated, taking small, frequent sips is often better than drinking large amounts of fluid at once.
You don’t have to drink just water. You can rehydrate with fluids like soup broth, juice, electrolyte drinks, or even milk.
Eat hydrating foods like fruits with a high water content. This can also be a great option for kids and older adults who have a hard time staying hydrated.
If you take medication or have a medical condition that affects your fluid balance, talk to your healthcare team about the optimal amount of fluids you need each day.
Frequently asked questions
High sodium levels mean that the ratio between sodium and water in your body is off. Sodium is one of many electrolytes in your blood that helps control fluid balance. Most of the time, high sodium levels happen because your body doesn’t have enough water — not because there’s too much sodium.
In severe cases, hypernatremia can be fatal. A serious but rare complication of hypernatremia is bleeding and swelling in the brain. This can lead to permanent brain damage or death. But this is very uncommon.
Yes, too much sodium can cause diarrhea. Anytime the fluid balance is off in your body, it can impact digestion. This includes high levels of sodium. This is because sodium attracts water, pulling it into your intestines from other parts of your body.
High sodium levels mean that the ratio between sodium and water in your body is off. Sodium is one of many electrolytes in your blood that helps control fluid balance. Most of the time, high sodium levels happen because your body doesn’t have enough water — not because there’s too much sodium.
In severe cases, hypernatremia can be fatal. A serious but rare complication of hypernatremia is bleeding and swelling in the brain. This can lead to permanent brain damage or death. But this is very uncommon.
Yes, too much sodium can cause diarrhea. Anytime the fluid balance is off in your body, it can impact digestion. This includes high levels of sodium. This is because sodium attracts water, pulling it into your intestines from other parts of your body.
The bottom line
A high sodium level is usually caused by severe dehydration. Most of the time, your body will protect you by telling you to drink more. But if you aren’t able to drink fluids when you need them, or your thirst mechanism is altered, you’re at a higher risk of this condition. Serious cases of high sodium levels need hospital-level treatment and close monitoring.
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References
Arampatzis, S., et al. (2012). Characteristics, symptoms, and outcome of severe dysnatremias present on hospital admission. The American Journal of Medicine.
Braun, M. M., et al. (2015). Diagnosis and management of sodium disorders: Hyponatremia and hypernatremia. American Family Physician.
MedlinePlus. (2020). Sodium blood test. National Library of Medicine.
Rolls, B. J., et al. (1990). Aging and disturbances of thirst and fluid balance. Nutrition Reviews.
Sonani B., et al. (2023). Hypernatremia. StatPearls.
