Hyperkalemia: Definition, Causes, Symptoms & Treatment

Instructor: Catherine Konopka

Catherine has taught various college biology courses for 5 years at both 2-year and 4-year institutions. She has a Ph.D. in cell and molecular biology.

Potassium plays a critical role in many systems of the human body. In this lesson, you will learn the causes and consequences of having too much potassium in your body.

Functions of Potassium

Potassium participates in many processes in the human body, including neurotransmission and muscle contraction. Its main role in these processes is in the establishment and maintenance of a negative resting membrane potential in the cell. It may seem odd, but every cell in the human body is electrically charged. Whenever there are a different number of charged particles on one side of the plasma membrane, or cell membrane, than the other, there is a voltage across the plasma membrane. In the case of potassium, there is a higher concentration of potassium ions (K+) in the cytoplasm compared to the outside the cell.

This potassium gradient, along with gradients for sodium, chloride, calcium and proteins, creates a negative resting potential inside the cell of about -70 mV. This negative resting potential is critical for the propagation of signals down axons of nerve cells. It is also critical for depolarization of muscle cells during muscle contraction. If anyone ion, be it potassium, sodium, calcium, etc, is not within its normal range, the resting potential will be either too high or too low. This will cause dysfunction of nerve impulses and muscle contractions - including the cardiac muscles of your heart!

Hyperkalemia Equals Too Much of a Good Thing

Hyperkalemia is abnormally high potassium levels in the extracellular (i.e. outside) fluid. This is in contrast to hypokalemia, which is an abnormally low level of potassium. To remember the difference between the prefixes hyper- and hypo-, visualize a hyper child that has had too much sugar. Another way is to remember the difference is that hypo- ends in an 'O' which looks a lot like a zero (0). Hyperkalemia is sometimes confused with hypercalcemia, which is abnormally high calcium levels. The Latin term for potassium is kalium, which is why the symbol for potassium on the periodic table is 'K'. So remember - the K in hyperkalemia is for potassium.

Normal conditions vs Hyperkalemia
Hyperkalemia is elevated potassium in the extracellular fluid

Causes and Symptoms

Hyperkalemia is typically caused by a loss in plasma membrane integrity or reduced secretion of potassium into urine by the kidneys. Most cells actively take-up potassium from the extracellular fluid to create the potassium gradient described above. If there is trauma to cells that disrupts the permeability of the plasma membrane, like in burn victims, potassium ions will leak out of cells. This will create higher levels of potassium in the extracellular fluid, thereby disrupting the potassium gradient for nearby cells.

It's the job of the kidneys to excrete any excess potassium into the urine. When the body senses elevated K+ levels, the hormone aldosterone signals to the kidneys to secrete more K+ into the urine. Thus if there are defects in kidney function or aldosterone signaling, the levels of K+ will remain too high. Also, several classes of drugs can alter potassium levels. It is technically possible to eat/drink too much potassium, but if you have properly functioning kidneys, it is unlikely you will develop hyperkalemia. So go ahead and eat as many bananas as you want.

Most of the symptoms of hyperkalemia are due to the neuron and muscle defects described above and include:

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