What is Hyperkalemia (High Potassium)? Meaning and Levels Defined


Hyperkalemia is a medical term that describes higher than normal levels of potassium (K+) in the blood. It is a common problem seen in clinical practice.

Hyperkalemia is defined as severe when the serum potassium levels rise too high ( above 7.0 mEq/kg).

Potassium is an essential electrolyte and a mineral. Its benefits on the body are tremendous and most importantly potassium is critical to the function of nerve and muscle cells, including those of your heart.

Hyperkalemia is caused by intake of excessive amount of potassium through potassium-rich foods, sizable tissue damage, certain medications and renal failure.

Low potassium in the body can have potentially dangerous complications and this condition can be life-threatening.

However, having too much potassium (severe hyperkalemia) too is bad. Luckily, most cases of hyperkalemia are of mild nature.

The most dangerous outcome of severe hyperkalemia is rapid and irregular heartbeats, which can be a life-threatening complication. It can lead to cardiac arrest and death. The mortality rate, if not treated immediately, is over 30%.

Having said that, it becomes imperative that severe hyperkalemia, when present, be treated at the earliest in the hospital.

Defining potassium levels in body and blood

The total body potassium stores approximately amount to 50 mEq/kg (about 3500 mEq in a 70-kg person).

98% of it is found inside the cells (described as intracellular) of the tissues, organs, etc. 75% of this intracellular potassium is found in muscle cells.

The balance of only 2% is present in the extracellular fluid and blood plasma.

This balance of intracellular to extracellular potassium is essential for the normal functioning of the neurons, skeletal muscles, and cardiac muscles.

That is why the normal range of serum blood potassium level is so narrow.

Normal potassium levels in the blood are between 3.6 to 5.2 millimoles per liter (mmol/L) or 3.5 and 5.0 milliEquivalents per liter (mEq/L).

Hyperkalemia is defined as a serum potassium concentration greater than about 5.0-5.5 mEq/L in adults.

Hyperkalemia is classified as mild (serum K 5.5–6.0 mEq/L), moderate (serum K 6.1–6.9 mEq/L ) or severe (serum K >7.0 mEq/L).

Clinical severity is determined by the speed of onset, the extent of the severity, and the development of clinical findings.

Levels greater than 7 mEq/L of severe hyperkalemia can lead to significant complications in the hemodynamic and neurologic functions.

Potassium levels exceeding 8.5 mEq/L can lead to respiratory paralysis or cardiac arrest and can immediately be fatal.

Classification of hyperkalemia: Acute and chronic

Hyperkalemia is classified as chronic or acute.

Acute hyperkalemia represents a single appearance that can spread over hours to days and usually treated as an emergency.

Chronic or recurrent hyperkalemia develops over weeks to months, is persistent or develops off and on, at least more than once in a year, and requires ongoing outpatient management. It is caused by the impairment of its excretion due to damaged kidneys and presents a chronic threat to patients with chronic kidney disease (CKD).

This post on their causes gives more detailed information.


The correct numbers of the incidence and prevalence of hyperkalemia are not known but are estimated to be 2% to 3% in the general population, and 1% to 10% among hospitalized patients.

People with heart failure, diabetes mellitus, CKD and those taking blood pressure medicines called renin-angiotensin-aldosterone system inhibitors (RAASi) have an estimated 2 to 3 times higher risk for hyperkalemia. RAASI drugs include beta blockers, renin inhibitors, angiotensin-converting enzyme (ACE) inhibitors, angiotensin receptor blockers (ARBs) and aldosterone inhibitors.

In addition, more than half of those patients approaching kidney failure and on predialysis care develop hyperkalemia.