Sodium and potassium are two electrolytes — minerals with an electric charge — that are required for the proper functioning of your cells. Your health care provider can do a test to check that you have normal sodium and potassium blood levels.
Read more: Foods Containing Electrolytes
Testing for Sodium and Potassium Blood Levels
Blood sodium and potassium levels are often checked as part of a basic metabolic panel or an electrolyte panel, along with other electrolytes, such as chloride and bicarbonate. A health care provider will take a blood sample from a vein in your arm. Typically, no special preparation is required before the test. Your health care provider will inform you if you need to temporarily stop taking any medications that could affect the results.
Your health care provider may order sodium and potassium blood tests as part of your regular checkup, to monitor an existing condition that affects electrolytes or if you have symptoms of abnormal potassium or sodium levels.
- Blood sodium and potassium levels are often checked as part of a basic metabolic panel or an electrolyte panel, along with other electrolytes, such as chloride and bicarbonate.
- Your health care provider may order sodium and potassium blood tests as part of your regular checkup, to monitor an existing condition that affects electrolytes or if you have symptoms of abnormal potassium or sodium levels.
Low Sodium: Hyponatremia
What Does a High Potassium Blood Level Mean?
In most cases of hyponatremia, "you have excess water in your body that has diluted the concentration of sodium," Dr. Weiner says. Hyponatremia may be caused by a range of conditions, including heart failure, kidney disease, adrenal problems, cirrhosis of the liver, and syndrome of inappropriate anti-diuretic hormone (SIADH), in which your body retains water instead of excreting it normally in your urine.cause:
- Hyponatremia may be caused by a range of conditions
- including heart failure
- kidney disease
- adrenal problems
- cirrhosis of the liver,
- syndrome of inappropriate anti-diuretic hormone (SIADH)
- in which your body retains water instead of excreting it normally in your urine
It can also be a side effect of certain medications, like diuretics and antidepressants.
High Sodium: Hypernatremia
An elevated blood sodium level is called hypernatremia.
Just as hyponatremia is usually the result of too much water, "if you have high sodium, then you are dehydrated — you have too little water," says Dr. Weiner. That may be due to lack of access to water or because the urge or ability to drink is impaired 6. In rare cases, it may be caused by excessive intake of salt.
Symptoms of an abnormally high blood sodium level include excessive thirst, urinating frequently, vomiting and diarrhea.
- An elevated blood sodium level is called hypernatremia.
- Just as hyponatremia is usually the result of too much water, "if you have high sodium, then you are dehydrated — you have too little water," says Dr. Weiner.
Low Potassium: Hypokalemia
Why Do I Always Crave Water & Salt?
According to the Mayo Clinic, hypokalemia is most commonly the result of losing too much potassium in the urine due to the use of diuretic medications that increase urination 23. It may also be caused by kidney disease, eating disorders, alcoholism, certain hormonal or genetic disorders or the loss of bodily fluids from diarrhea, vomiting and sweating.cause:
- It may also be caused by kidney disease
- eating disorders
- certain hormonal or genetic disorders or the loss of bodily fluids from diarrhea
Laxatives and certain antibiotics may also cause low potassium levels.
High Potassium: Hyperkalemia
Hyperkalemia is most commonly caused by a problem with the kidneys. If the kidneys aren't able to remove the proper amount of potassium, it can build up in the blood. High potassium levels can also result from conditions including Addison's disease, type-1 diabetes, certain genetic disorders and burns or other traumatic injuries. It can also be a side effect of certain diuretics, antibiotics and blood pressure lowering drugs.
According to the Mayo Clinic, a potassium blood test will often come back with a falsely high level because the blood cells in the blood sample ruptured 23. A repeat test will be done if this suspected.
Read more: Symptoms of Potassium Overdose
- A higher-than-normal level of potassium in the blood is called hyperkalemia 2 is a life-threatening condition that usually requires immediate treatment.
What Does a High Potassium Blood Level Mean?
Why Do I Always Crave Water & Salt?
Causes of Low Sodium Levels in the Body
Does Sodium and Potassium Imbalance Lead to Swollen Ankles?
Does Low Sodium & High Potassium Have Anything to Do With Addison Disease?
Electrolyte Imbalance and Burning Urine
Low Blood Pressure & Craving Salt
Salt Substitute Health Risks
Can Low Potassium Cause Death?
Blood Tests to Check Your Metabolism
- U.S. National Library of Medicine: "Sodium Blood Test"
- Mayo Clinic: "High Potassium (Hyperkalemia)"
- Mayo Clinic: "Low Potassium (Hypokalemia)"
- U.S. National Library of Medicine: "Potassium Blood Test"
- U.S. National Library of Medicine: "Low Potassium Level"
- UptoDate: "Etiology and Evaluation of Hypernatremia in Adults"
- Dylewski JF, Linas S. Variability of potassium blood testing: Imprecise nature of blood testing or normal physiologic changes? Mayo Clinic Proceedings. 2018. 93(5):551-554. doi:10.1016/j.mayocp.2018.03.019
- Friedman PA, Scott CG, Bailey K, et al. Errors of classification with potassium blood testing: The variability and repeatability of critical clinical tests. Mayo Clinic Proceedings. 2018;93(5):566-572. doi:10.1016/j.mayocp.2018.03.013
- Galloway CD, Valys AV, Shreibati JB, et al. Development and validation of a deep-learning model to screen for hyperkalemia from the electrocardiogram. JAMA Cardiology. 2019. 4(5):428-436. doi: 10.1001/jamacardio.2019.0640
- National Heart, Lung, and Blood Institute. Blood tests.
- Ialongo C, Bernardini S. Phlebotomy, a bridge between laboratory and patient. Biochem Med (Zagreb). 2016;26(1):17–33. doi:10.11613/BM.2016.002
- Schmidt ST, Ditting T, Deutsch B, et al. Circadian rhythm and day to day variability of serum potassium concentration: A pilot study. Journal of Nephrology. 2015. 28(2):165-72. doi:10.1007/s40620-014-0115-7
- Chatterjee R, Yeh HC, Shafi T, et al. Serum potassium and the racial disparity in diabetes risk: the Atherosclerosis Risk in Communities (ARIC) Study. American Journal of Clinical Nutrition. 2011. 93(5):1087-91. doi:10.3945/ajcn.110.007286
- Cleveland Clinic. Hyperkalemia (high blood potassium). Updated October 19, 2016.
- Cleveland Clinic. Low potassium levels in your blood (hypokalemia). Updated March 12, 2018.
- Kardalas E, Paschou SA, Anagostis P, et al. Hypokalemia: a clinical update. Endocrine Connections. 2018;7(4):R135-R146. doi:10.1530/EC-18-0109
- Cleveland Clinic. Low potassium levels in your blood (hypokalemia): Management and treatment. Updated March 12, 2018.
- Bnaya A, Ruchlemer R, Itzkowitz E, Gabbay E, Shavit L. Pseudohyperkalemia in chronic lymphocytic leukemia. American Journal of Medicine. 2020;133(2):e52-e53. doi:10.1016/j.amjmed.2019.07.037
- Ben Salem C, Badreddine A, Fathallah N, Slim R, Hmouda H. Drug-induced hyperkalemia. Drug Safety. 2014. 37(9):677-92. doi:10.1007/s40264-014-0196-1
- Cleveland Clinic. How can hyperkalemia (high blood potassium levels) be treated? Updated October 19, 2016.
- Miller KC. Plasma potassium concentration and content changes after banana ingestion in exercised men. J Athl Train. 2012;47(6):648–654. doi:10.4085/1062-6050-47.6.05
- American Association for Clinical Chemistry. Potassium. Updated 12/13/19.
- Jameson JL, et. al. Harrison's Principles of Internal Medicine, 20th Edition. McGraw Hill Education. 2018.
- Kovesdy CP, Appel LJ, Grams ME, et al. Potassium homeostasis in health and disease: A scientific workshop cosponsored by the National Kidney Foundation and the American Society of Hypertension. Journal of the American Society of Hypertension. 2017;11(12):783-800. doi:10.1016/j.jash.2017.09.011
- Nilsson E, Gasparini A, Arnlov J, et al. Incidence and determinants of hyperkalemia and hypokalemia in a large healthcare system. International Journal of Cardiology. 2017;15;245:277-284. doi:10.1016/j.ijcard.2017.07.035
- Pagana KD, Pagana TJ, Pagana TN. Mosby’s Diagnostic & Laboratory Test Reference. 14th ed. St. Louis, Mo: Elsevier; 2019.
- Schrier RW. Renal and Electrolyte Disorders, 8th Edition. LWW. 2017.
- Shrimanker I, Bhattarai S. Electrolytes. in: StatPearls. Updated January 20, 2020.
Michael Gray has been writing since 2006. He has authored a book entitled, "Sleep with this Book: A step-by-step guide to becoming a Certified Registered Nurse Anesthetist (CRNA)." Gray has been in the medical field for 10 years. He has a Bachelor of Science in nursing from the University of Memphis.