High Blood Potassium Test – Causes

Although this website is about high potassium foods, people often ask about what to do for a high blood potassium level, called hyperkalemia. This is not a question that should be answered on the internet. A high level of potassium in the blood stream is dangerous and potentially deadly. A person's physician must be the one to manage the condition. The article to be discussed today (1) was written to help physicians with this situation. But the first portion of the article has information that is understandable and may be interesting to a nonphysician. This post is not to be used for self-diagnosis, but is to provide some basic understanding of how someone can have a high blood potassium level. And why a simplistic answer on the internet should be rejected.

What The Blood Potassium Test Is

Blood Test VialsThe blood potassium test measures the level of potassium in the portion of the blood that has no cells. The level of potassium inside cells is much higher than in this portion of the blood. If any cells burst and release their inner contents into the blood, the potassium level in the blood will rise. If the blood potassium level is high, but no cells have burst, the level rises because the cells in the body are not moving the potassium in and out of the cells quickly enough.

It is quite rare for healthy persons to develop a high potassium level in their blood. However, people may have conditions that they are unaware of, or they may be unaware that they did something to cause a high blood potassium level. The publication (1) featured in this post discusses many of the various causes of a high blood potassium level. It also discusses how bodily processes lead to this elevation. It does not discuss the change in the cell membrane potential that results from a poor ratio of potassium to sodium. Nor does it discuss the long term consequences of a poor potassium to sodium ratio.

How Potassium Balances

The beginning of the publication discusses how potassium adjusts itself in the body. The authors discuss the normal balancing of potassium. They discuss that normally potassium is much higher inside the cell than in the blood. The natural flow of potassium would be out of the cell except for an enzyme known as sodium potassium ATPase (Na-K-ATPase). This enzyme is also known as the sodium pump or sodium potassium pump. It is a pump that pushes sodium out of the cell and potassium back into the cell against their normal concentration gradients.

This allows the cells to maintain their normal resting membrane potential (electrical field). This field changes quickly in nerve and muscle cells when they perform their normal functions. But this field also is important in multiple other cells. Although the authors do not discuss the other cells, the change in electric field may well be critical to the function of every cell. Multiple investigations have shown how it is critical in many secretory cells, as discussed in this post.

The authors describe that after a meal that is rich in potassium, insulin is secreted in response to the increased level of glucose in the blood. The insulin increases the sodium pump activity and results in the extra potassium in the blood stream being driven into the cell to create the proper balance of potassium and sodium inside and outside the cell. The increased potassium in the blood also leads to an increased secretion of aldosterone, which promotes potassium excretion in the kidney and in the colon. We discussed in more detail how aldosterone does this in the kidney in a prior post.

False Test Result Of High Potassium

The first part of the discussion about high blood potassium levels is about how the test can give a falsely high result. The test can show a high potassium level when the potassium level in the patient is really normal. The most common reason for such a falsely high blood test is a bursting of the red blood cells when the blood is drawn. The red blood cells may burst from excessive use of the tourniquet during the blood draw, or from the way the sample is handled after it has been drawn. For example, squirting the blood into a collection vial under high pressure will result in bursting of the red blood cells. Another cause of a false test is a rare red blood cell disease that can cause a release of potassium in the test tube that does not occur in the patient. A third possible cause of a falsely high blood level occurs when other blood cells besides the red blood cells are present in large numbers in the blood.

How Potassium Can Be High In Blood

The authors then discuss the various causes of a true rise of potassium in the blood. They divide the causes into 3 major categories. The first is increased potassium intake. The second is increased release from inside cells. And the third is decreased potassium excretion by the kidneys.

Too Much Potassium In Food

The first causes that the authors discuss are related to consuming too much potassium. In someone with healthy kidney function there is no problem from food. However if the kidney function is impaired, excessive potassium in food can lead to a life-threatening condition. This is the most common cause of excessive potassium in the blood stream of people with end-stage kidney disease.

For people with a normal kidney, the release of potassium from even high potassium foods is slow enough that the kidneys can prevent an excessive build-up. However, if the potassium ingested is in a form that is quickly absorbed, it can raise the blood level of potassium quickly. This is the reason that the amount of potassium allowed in medical pills is limited. Other possible sources of quickly absorbing potassium include salt substitutes, supplements and concentrated liquids. Although normal kidneys can quickly bring down the potassium level, if the high level results in a heart rhythm irregularity it can be deadly in a few minutes.

Potassium Release From Cells

The authors then discuss the conditions leading to excessive release of potassium from cells and inadequate excretion by the kidney. These are situations that would be of more interest to doctors, and less so to lay persons. There are certain medical treatments that may cause a rise in potassium. For example, transfusions of blood or blood products that are older (generally more than 3 weeks old) may lead to a high level of potassium in the blood stream because the cells being transfused begin to break down.

Other conditions in which cells breakdown likewise may lead to a high level of potassium in the blood stream. Examples include sudden death of a large number of tumor cells, death of intestine or muscle from loss of blood supply, breakdown of blood cells in a collection of blood outside blood vessels caused by a traumatic injury, or hypothermia (a large drop in body temperature from cold exposure).

Certain medications can raise the blood potassium level. One group of medications that do this are those that inhibit the sodium potassium ATPase pump. Another set of medications are those that are used during general anesthesia to relax the muscles. Such medications that can potentially lead to an increase in potassium in the blood stream are carefully monitored, especially when a patient has other conditions that can also raise the blood potassium level.

Other conditions leading to excessive potassium release from the cells include extreme physical exercise, some conditions of diabetics, and a particular genetic disorder. Physical exercise normally leads to an increase in the potassium level in the local muscle area being exercised. The exercise also causes a smaller rise of potassium throughout the blood system. However this level lowers within a few minutes. Another common condition is when diabetics get out of control and they develop ketoacidosis. And yet another type of disorder leading to excessive release of potassium from cells is a type of periodic paralysis that is a genetic disorder.

Kidney Disease

Among the most common conditions associated with a high level of potassium are those that involve kidney dysfunction. Chronic kidney disease can lead to a high level of potassium once the kidneys are able to filter only limited amounts of fluid. When this condition progresses to complete failure, a high level of potassium in the blood develops that requires correction with dialysis. One condition that leads to problems with the kidneys' ability to handle potassium is when the blood volume is too low, such as with severe dehydration or blood loss. But there are other conditions related to blood volume that can lead to kidney dysfunction. Sometimes even when blood volume is adequate, the plasma volume will be too low. This happens when there is liver failure or heart failure.

Aldosterone's Role

Another cause of the kidney being unable eliminate potassium occurs when the action of aldosterone is decreased. There are two main reasons the action of aldosterone may be decreased. It may be that aldosterone cannot have its normal effect on the kidney, even though the aldosterone blood level is adequate. Or it may be that not enough aldosterone is produced by the adrenal gland. Aldosterone is important for producing the channels in the kidney cells that help excrete potassium. However when someone has Addison's disease, his adrenal gland is incapable of producing aldosterone because the adrenal gland is defective. Not enough channels are made in kidney cells and potassium does not get eliminated.

Sometimes the adrenal gland is normal but it cannot produce aldosterone, because it does not have the proper stimulation from other hormones. A relatively common cause of not enough aldosterone being produced occurs in elderly diabetics that have some kidney disease. In this case the elderly do not produce enough renin. This is called hyporeninemic hypoaldosteronism.

Another reason that aldosterone may not have its normal effect on the kidney comes from medications that interfere with aldosterone's action on the kidney cells. These include the ACE inhibitors (common antihypertensive medications), as well some other antihypertensive medications. Two other types of interfering medications are NSAIDs (non-steroidal anti-inflammatory drugs) and cyclosporine.

Sometimes the kidney acquires damage which leads specifically to resistance to the aldosterone action without causing the kidney to fail in its filtering function. This damage involves the cells that are lining the excretory tubules of the kidney. Usually this occurs because the tubules become blocked or inflamed.

Sometimes It's Genetic

Finally, the authors discuss two of the main genetic problems that can lead to high blood levels of potassium. These genetic abnormalities lead to defective production of aldosterone, or defective production of the channels involved in potassium excretion by the kidney cells. There are several enzymes that are involved in the production of aldosterone. If any of these enzymes are not produced properly, then aldosterone will not be made. Likewise the channels in the kidney cells which allow potassium to be excreted must be made properly. If any of the components of these channels are defectively produced because of a genetic defect, they will not function and potassium will build up in the blood stream.

So this is a very good article for those who are interested in all the various causes of an increased level of potassium in the blood stream. This may help those who ask what they should do about a high level of potassium in the blood stream to realize that it is not a simple one sentence answer. It is not a question that should be answered on the internet. Anyone who has a high level of potassium in the blood stream has a dangerous and potentially deadly condition. They must contact their physician for advice. It takes a knowledge base that is far more extensive than what has been discussed in this post to discover the reason for a high potassium blood level and to correct it.
1. Differential diagnosis of hyperkalemia: an update to a complex problem. Eleftheriadis T, Leivaditis K, Antoniadi G, Liakopoulos V. Hippokratia. 2012 Oct;16(4):294-302.