A 38-year-old male asked:
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if the majority of potassium in the body is in red blood cells and very little in serum why is serum potassium level used to diagnose hypokalemia?

3 doctor answers
Dr. Calvin Weisberger
50 years experience Cardiology
Potassium: Electrolytes are in balance between intra and extracellular spaces. If the serum potassium is low, then even though intracellular potassium is higher, the total body potassium is down. When serum potassium is too high or too low, serious systemic problems result.
Answered on Mar 19, 2013
Dr. Michael Dugan
Specializes in Hematology
Becuase it can : Be measured quickly, safely, and with good accuracy. Not such a method to determine intracellular electrolyte levels.
Answered on Dec 9, 2013
Dr. Ed Friedlander
43 years experience Pathology
It's what matters: The serum potassium is in equilibrium with the tissue concentrations, which must be maintained within a very narrow range for the heat to be able to maintain its beat. Your question is a good one and reflects a common misunderstanding. It's not the total body potassium that matters, just the amount that's actually affecting the electrical system outside the heart & brain cells.
Answered on Apr 11, 2016
1
1 comment
Dr. Clarence Grim
56 years experience Endocrinology
Majority is actually in muscle cells and all other cells not just red cells.But if reds cells are broken in the blood sample that is taken from you the apparent K level will be read as high depending on how much is released from broken red cells Common in those who are difficult to draw blood from.
Apr 11, 2016

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Dr. Thomas Namey
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Dr. Ed Friedlander
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Of COURSE: Basic biology, Matt. Magnesium and potassium are cations that are concentrated by the body inside of cells rather than outside.
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Dr. Liawaty Ho
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Serum potassium: Bmp will show you serum potassium level. Hypokalemia is diagnosed if the serum potassium level is below the normal range.
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