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Normal potassium levels in the blood are 3.7–5.2 mmol/L.
Potassium is an important electrolyte in the body that plays a role in many functions. Having a potassium level that is too low (hypokalemia) and having a potassium level that is too high (hyperkalemia) are both very dangerous and can lead to weakness, muscle cramping, and death.
High potassium, in particular, can cause heart rhythm problems that are fatal. Potassium levels are regulated by the kidneys and can be affected by certain medical conditions (such as kidney disease) or by taking certain medications (such as diuretics). Potassium levels can be raised with oral or injectable potassium; potassium levels can be lowered with a variety of medications.
What we mean by normal
In medicine, using the term “normal” can sometimes be off-putting. Saying something is “normal” implies that everything else is “abnormal.” Additionally, saying something is “normal” may not be accurate, since something that is “normal” for you may not be “normal” for somebody else. Therefore, instead of saying certain values are “normal,” alternative terminology may be to say that these values are “healthy” or “within the reference range.”
Additionally, some values have well-defined cutoffs, while others do not. For example, when looking at hemoglobin A1c levels, a value of 6.5 or greater is always diagnostic of diabetes. On the other hand, when looking at testosterone levels, some use cutoffs of 270–1,070 ng/dL while others use cutoffs of 300–1,000 ng/dL.
The information above represents values that are commonly used as cutoffs. However, depending on the specific source you’re looking at or the laboratory you go to, their values may be a little different.
Dr. Tzvi Doron is Board Certified in Family Medicine by the American Board of Family Medicine and is Ro's Chief Clinical Officer.