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Low or High Sodium? Blood Test, Causes, & Ways to Improve

Written by Biljana Novkovic, PhD | Last updated:
Jonathan Ritter
Puya Yazdi
Medically reviewed by
Jonathan Ritter, PharmD, PhD (Pharmacology), Puya Yazdi, MD | Written by Biljana Novkovic, PhD | Last updated:

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Sodium is an essential element in the blood, which plays an important role in water-electrolyte balance, blood pressure, muscle, and nerve function. Keep reading to find out what low or high sodium levels mean, and how you can increase or decrease them.

What is Sodium?

Sodium is a positive ion and one of the body’s main electrolytes, which are minerals we need in relatively large amounts. It plays vital roles in controlling blood pressure, fluid balance, and the acid-base balance in the blood. In addition, sodium is needed for proper nerve and muscle function [1].

Table salt (sodium chloride) and the natural salt content in foods are the main sources of sodium in the diet. Adults need less than 500 mg sodium/day in order to maintain normal sodium levels in the body. However, 95% of the world’s population consumes between 3 and 6 g/day, which is much more than necessary [1, 2].

Healthy sodium levels in the body are maintained in a narrow range by [1, 3, 4]:

  • Hormones that increase (natriuretic peptides) or decrease (aldosterone) kidney excretion of sodium through urine
  • Hormones that prevent the loss of fluids together with sodium (antidiuretic hormone)
  • Thirst. Normally, even a very small (2–3%) increase in blood sodium induces thirst, and sodium levels go back down to normal once the person drinks water

Dietary sodium deficiency is extremely rare, even among people on very low sodium diets. Sodium levels may fall below normal under extreme conditions of heavy and continued sweating, or in cases of heavy injury, chronic diarrhea, or kidney disease where the body is unable to hold onto sodium [1, 2].

Blood sodium can increase above normal when people don’t drink enough water or have an excessive salt intake. It can also increase due to health issues such as kidney disease. Elevated sodium is more common in the elderly, because of a decline in kidney function and a lower intake of liquids [5, 6, 7].

Normal Range

Sodium levels are often measured as part of a complete metabolic panel, which provides doctors important information about your overall health.

Normal levels of blood sodium range from 135 to 145 mEq/L or mmol/L [8].

Levels below 135 mEq/L are called hyponatremia, whereas levels above 145 mEq/L are called hypernatremia [8].

Low Sodium (Hyponatremia)

When sodium levels are low, this is called hyponatremia (“hypo”= less than normal, “natremia”= sodium in the blood).

A result that’s lower than normal, doesn’t necessarily mean that you have a health condition needing treatment. Your doctor will interpret your result, taking into account your medical history, symptoms, and other test results.

Hyponatremia is classified as [9, 10]:

  • mild (130 to 134 mmol/l)
  • moderate (125 to 129 mmol/l)
  • severe (<125 mmol/l)

Further, hyponatremic disorders are divided into euvolemic, hypervolemic, and hypovolemic, based on the amount of fluid in the body [9, 10].

Causes shown here are commonly associated with low sodium levels. Work with your doctor or another health care professional to get an accurate diagnosis.

Causes

These can decrease sodium levels:

  • Vomiting or diarrhea [11]
  • Blood loss due to injury [12]
  • Chronic alcohol use, of beer in particular [13, 14]
  • Excessive water intake, often associated with endurance exercise (e.g. in marathon runners) [14]
  • Malnourishment or low salt intake, often in those with low-protein, high-water diets [14]
  • Excessive thirst (polydipsia) caused by psychiatric illness or diabetes [14]
  • Liver disease, kidney disease, or heart failure [14]
  • Severe hypothyroidism [15]
  • Aldosterone deficiency caused by adrenal insufficiency, due to genetic disorders, issues with adrenal gland, pituitary, or hypothalamus (e. g. Addison’s disease) [14, 16]
  • Some other conditions, such as syndrome of inappropriate ADH release (SIADH) and cerebral salt wasting (CSW) [14]

Drugs that can decrease sodium levels include:

  • Water pills (diuretics), which help the kidneys get rid of excess water. These are often used to treat high blood pressure [17, 14]
  • Antidepressants [18]
  • Heparin, an anticoagulant used to treat blood clots [19, 20]
  • Ecstasy (MDMA) [14]

Symptoms

Symptoms of low sodium include [14, 21]:

  • Nausea
  • Vomiting
  • Headaches
  • Loss of appetite
  • Confusion

Increasing Blood Sodium

The most important thing is to work with your doctor to find out what’s causing your low sodium and to treat any underlying conditions!

Treatment will depend on the type of hyponatremia and its severity.

Discuss the additional lifestyle changes with your doctor. None of these strategies should ever be done in place of what your doctor recommends or prescribes!

Drink water in moderation. Drinking too much water will further decrease your sodium levels. If you are sweating excessively due to exercise or sauna, make sure to replenish your electrolytes as well as water. Weighing before and after an athletic event can tell you how much fluids you need. Otherwise, use thirst and the color of your urine as guidance – if you’re not thirsty and your urine is pale yellow, it’s likely you are getting enough water [14, 22, 23, 24].

Avoid drinking alcohol, especially beer, as this will further decrease your sodium levels [13, 14].

Increase your salt (sodium chloride) intake [25].

Make sure you are getting enough protein in your diet (if your kidneys are healthy). Low protein diets, that are not uncommon in the elderly, can make it harder for the kidneys to remove excess water [25, 26].

High Sodium (Hypernatremia)

High sodium levels are called “hypernatremia” (“hyper”= more than normal, “natremia”= sodium in the blood) [27]. Hypernatremia means you have a deficit of water in relation to sodium in the blood/body.

However, a result that’s higher than normal, doesn’t necessarily mean that you have a health condition needing treatment. Your doctor will interpret your result, taking into account your medical history, symptoms, and other test results.

People at a higher risk of hypernatremia are infants, seniors, hospitalized patients, and people suffering from mental illnesses. Hypernatremic disorders are divided into euvolemic, hypovolemic, and hypervolemic hypernatremia [28, 29].

Causes shown here are commonly associated with high sodium levels. Work with your doctor or another health care professional to get an accurate diagnosis.

Causes

High sodium levels can be caused by:

  • Not drinking enough water, especially during strenuous exercise [5, 30]
  • Losing too much water due to sweating, fever, diarrhea, or vomiting [5]
  • Excessive salt or sodium bicarbonate (baking soda) intake [6, 7]
  • Chronic alcohol consumption [31]
  • Altered mental state, dementia, delirium, or brain damage that decrease thirst and water consumption [6]
  • Kidney disease [3, 32]
  • Excess of adrenal hormones cortisol and aldosterone (e.g. hyperaldosteronism, Cushing’s syndrome) [6]
  • Diabetes insipidus, a rare condition in which the kidneys are unable to prevent the loss of water [5]
  • Too much licorice [33, 34]
  • Aging, associated with a decline in kidney function and a lower intake of liquids [6]

Drugs that can increase sodium levels include:

  • Antibiotics [35]
  • Corticosteroids (hydrocortisone, prednisone), used to treat a variety of inflammatory conditions and diseases [36]
  • Laxatives [37]
  • NSAIDs [38]

Symptoms

Symptoms of high sodium levels include [5]:

  • Intense thirst
  • Muscle weakness
  • Restlessness
  • Nausea
  • Vomiting

Decreasing Blood Sodium

The most important thing is to work with your doctor to find out what’s causing your high sodium and to treat any underlying conditions!

Discuss the additional lifestyle changes listed below with your doctor. None of these strategies should ever be done in place of what your doctor recommends or prescribes!

Lower your salt intake. Avoid foods high in sodium, such as breads, cheeses, and processed foods in general [7, 39]. Reducing your salt intake can be beneficial even when your sodium returns to normal [40].

Drink enough water as this will help in diluting the high sodium concentration [7].

Discuss using a salt substitute that contains potassium chloride with your doctor. These shouldn’t be used if you have a medical condition such as diabetes or kidney disease, or if they interfere with your medications [41].

About the Author

Biljana Novkovic

Biljana Novkovic

PhD
Biljana received her PhD from Hokkaido University.
Before joining SelfHacked, she was a research scientist with extensive field and laboratory experience. She spent 4 years reviewing the scientific literature on supplements, lab tests and other areas of health sciences. She is passionate about releasing the most accurate science and health information available on topics, and she's meticulous when writing and reviewing articles to make sure the science is sound. She believes that SelfHacked has the best science that is also layperson-friendly on the web.

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