What are normal blood sodium levels and what it means if they are too low or too high

normal sodium levels — Your doctor may order a sodium blood test as part of an electrolyte panel.
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Normal sodium levels in your blood are between 135 and 145 milliequivalents per liter (mEQ/L).
This measures how much sodium is able to interact with other molecules in your blood, so that your water levels remain regulated.
High sodium levels are often caused by dehydration or kidney disease, whereas low sodium levels may be caused by diarrhea and vomiting and are most common in older adults.
This article was medically reviewed by Jason R. McKnight, MD, MS, a family medicine physician and clinical assistant professor at Texas A&M College of Medicine.
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A sodium blood test will tell you if your blood sodium levels are normal. Blood sodium levels actually have little to do with how much sodium you consume and are tightly regulated by your body’s internal processes.

An imbalance in your blood sodium levels can be caused by factors like adrenal gland issues, dehydration, and some medications. Here’s what you need to know about what your blood sodium levels should be and how you can test them.

The purpose of a sodium blood test

“The sodium concentration is part of a panel of blood chemistry values that doctors obtain routinely,” says Richard H. Sterns, MD, a professor of medicine at the University of Rochester.

A doctor may evaluate your sodium blood levels, “on admission to the hospital or during a routine check-up, even when they don’t necessarily suspect something,” Sterns says. Your doctor may also order a sodium blood test if you have symptoms of an electrolyte imbalance in your blood, which can be a sign of a condition like cancer or a hormone deficiency, Sterns says.

Electrolytes, like sodium, are minerals that help control the nervous system function and balance pH levels in the body. If your sodium levels are too high, you may show symptoms like excessive thirst or urinating infrequently. If your sodium is too low, you may have confusion, weakness, and muscle twitching.

Sodium, in particular, helps regulate the amount of water in your body and keeps your muscles and nerves running properly. The concentration of sodium in your blood acts as a signal to your body about whether the amount of fluid in your blood is normal. If your blood volume is too low or too high, your kidneys will excrete or retain sodium to get your fluid levels back in balance.

Your body keeps a careful balance of sodium in your blood but your sodium levels can be affected by your water intake, illnesses like diarrhea, and some medications. This is because some of these conditions can make you lose water without losing sodium or vice versa, leading to an imbalance in your blood volume.

Having the right amount of fluid in your blood is important because too much or too little can shrink or grow the structure of your cells and cause damage to your nerves and muscles. For this reason, having a sodium imbalance can lead to dangerous complications like changes in blood pressure and even brain swelling.

"A markedly abnormal sodium concentration can affect the brain," Sterns says. This means that if your sodium levels become extremely high or low, you may have dangerous effects like confusion, slurred speech, seizures, or coma, Sterns says. If you start to experience any of these symptoms, you need to get medical attention immediately.

What are normal sodium levels?

A normal level of sodium in your blood is between 135 and 145 milliequivalents per liter (mEQ/L), which measures how much sodium is available to interact with other molecules in your blood, allowing it to effectively regulate your water levels. Anything above or below this range is considered abnormal and can be harmful to your body.

Low sodium levels

Low sodium levels, also known as hyponatremia, occurs when your blood sodium levels fall below 135 mEQ/L.

This condition is most common in older adults and in severe cases, it can cause dangerous effects like seizures or coma. Because when the sodium in your bloodstream becomes diluted, your body's water levels increase and your cells swell up and become damaged, which can causing serious problems with your body functions. In most cases, you may have milder symptoms like headache, nausea, and muscle aches, but if you think you have hyponatremia, you should always get medical attention right away.

Hyponatremia is relatively common – 1.7% of Americans experience hyponatremia and it is the most frequent abnormality seen in hospital patients' blood tests. Causes of low sodium levels include:

Diarrhea and vomiting
Drinking too much water, particularly during athletic events like a marathon
Adrenal gland issues
Heart failure
Kidney or liver disease
Some diuretic or pain medications

"Alcoholics who drink a lot of beer are particularly susceptible to hyponatremia as are users of the recreational drug Ecstasy," Sterns says. Inexperienced athletes may also drink too much water and develop hyponatremia. If you are in a sporting event, it's best to only drink when you are thirsty, as "excessive water ingestion is more dangerous than dehydration," Sterns says.

If you have more mild, chronic hyponatremia caused by conditions like liver or kidney disease, your doctor may recommend lifestyle changes like cutting down your fluid intake or adjusting any medications that influence your sodium levels.

If you develop sudden, severe hyponatremia, you may need emergency treatment such as getting intravenous sodium-rich fluids.

High sodium levels

High sodium levels, also called hypernatremia, occurs when your blood sodium levels rise above 145 mEQ/L. More mild hypernatremia will usually just make you extremely thirsty, but in more severe cases, it can lead to seizure or stroke.

Up to 1% of people in the hospital at any given time experience abnormally high sodium levels. Hypernatremia may be caused by:

Dehydration
Problems with your adrenal gland
Certain medications like laxatives or lithium
Severe diarrhea and vomiting
Kidney disease
Complications of diabetes

If you are not vomiting or having severe, life-threatening symptoms, hypernatremia can be treated by drinking fluids to help dilute the levels of sodium in your blood, but more severe cases may require you to rehydrate through an IV drip.

How to determine your sodium levels

The amount of sodium in your bloodstream can provide important information about your health. For example, your sodium levels can reflect your diet, as it measures the balance between the amount of water and the amount of sodium you take in through food and drinks.

Your blood sodium levels also offer insight into how much sodium comes out through your urine – this can help a doctor understand how organs like your kidneys and heart are working.

You can find out your sodium levels through both blood and urine tests. Your doctor may order a sodium test as part of a general blood test for glucose levels, electrolytes, or kidney function. If your sodium levels are abnormal in the blood test results, your doctor may follow up with a urine test to check if you have kidney damage or other serious conditions.

A blood test will take place at a doctor's office but your doctor may ask you to take a urine test at home to collect your urine each time you urinate over the course of 24 hours before sending it out to a lab.

Takeaways

Your body works hard to keep your sodium and water levels in balance, but certain conditions can disrupt your normal sodium levels, causing harmful effects. If you think you are at risk for sodium imbalance, ask your doctor about getting a blood test. If you are having sudden symptoms of a sodium imbalance, get medical attention immediately.