When a person has kidney disease, their body can start to have trouble managing potassium levels. Potassium levels that are too high or too low can cause problems with your heart beat – which can be very serious.
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For this reason, many people with kidney disease monitor their potassium labs and potassium intake very closely. But did you know that your potassium labs could be wrong?
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What is pseudohyperkalemia?
Hyperkalemia is the official term for high potassium levels in your blood. Hyper means ‘high’. Kale comes from the latin word for potassium ‘kalium’, and then ‘emia’ just means blood. String them all together and you’ve got hyperkalemia.
Pseudo-hyperkalemia is a term used to describe a situation when your potassium lab results say that you have high potassium levels in your blood, but you really don’t. It’s not a real high potassium level. The lab result does not represent your true potassium levels.
Why does pseudohyperkalemia matter?
As a dietitian, I hate to see people limiting their potassium intake when they don’t have to. There are so many wonderful foods out there that can truly help you manage your kidney disease better (and other conditions too!), but they happen to have more potassium in them than people think they can have.
But if your potassium level is high, it can be hard to appreciate the benefits of certain higher potassium foods like fruits and vegetables. That’s why it is incredibly important to get an accurate potassium lab value.
What causes psuedohyperkalemia?
There are several things that can pseudohyperkalemia, but in this article, I’m going to focus on one of the EASIEST mistakes that I see people make that causes their potassium levels to be falsely elevated.
Clenching your fist during lab draws is one of the most common ways people with CKD cause pseudohyperkalemia.
Fist clenching! You read that right. We’ve all done it. We roll up our sleeve, and then we all instinctively make a fist in an effort to make our veins easier to find. Sometimes, we are even given a ball to squeeze. And the more you squeeze, the higher your potassium levels will be!
In one study of fist clenching and potassium levels, the potassium lab went up by 2.7 mEq/L! That is a HUGE increase in potassium. Imagine if your potassium lab came back at a 6.7 (which is very high!), but it was really supposed to be 4.0 (which is well within the range of normal!). What changes would you make in your diet?
I bet you would almost immediately cut out every single fruit and vegetable in your diet – and probably even more healthful foods like beans and whole grains! And these are foods that will actually help protect your kidneys and make it easier to manage potassium (yes, eating more fruits and vegetables can actually make it easier to manage your potassium levels – and you should consider signing up for one of our courses to learn how to manage your potassium levels the right way).
And just in case you are wondering, yes, the person whose potassium shot up by 2.7meQ was squeezing pretty hard. However, the researcher made a point of saying that even minor squeezing or clenching still resulted in potassium levels increasing by 0.5mEq, which could still be a meaningful change if your potassium levels are just a little out of range.
How does fist clenching cause high potassium levels?
About 98% of the potassium in your body is located inside your cells, while only 2% of potassium is floating around in your blood. It is estimated that there are about 130,000mg of potassium in the average body, which means that there are more than 127,000mg of sodium inside your cells.
Sometimes, the potassium that is INSIDE your cells, can get OUTSIDE of your cells (and into your blood stream). One of the ways that this can happen is when you use the muscles in your body. Squeezing your muscles (even the small muscles in your forearm), will temporarily release a bit of potassium into your blood. It’s just temporary, and it is completely normal. In the grand scheme of things, it isn’t even a lot of potassium that is being released.
However, because you probably have a tourniquet around your arm, the potassium has nowhere to go except into the blood sample tube – which makes you look like you have a high potassium level!
How can I prevent pseudohyperkalemia?
Don’t make a fist when you get your labs drawn! Using a tourniquet is fine, but try to avoid making a fist or squeezing your hand or arm muscles during the lab draw.
If for some reason the person drawing the labs needs you to make a fist to help find your veins, then insist that they draw your electrolyte labs LAST.
Typically, when getting labs done, you’ll have more than one test tube of blood taken, and they usually remove the tourniquet after puncturing your vein. Once your blood is able to flow normally, the potassium released from fist clenching will start to spread out. If the technicians are able to draw other labs first, and then do your potassium lab last, you’ll have a better chance of having an accurate reading.
There are MANY other things that you can do to help control potassium levels (including some additional quick and easy ways to prevent pseudohyperkalemia), and many of them have nothing to do with how much potassium is in your food (yes, I know how crazy that sounds). Don’t assume that restricting potassium intake is the best way to control your potassium levels. In many ways, this can actually be harmful to your kidneys. Learn more about managing your potassium with our expert created courses or book a session with a board certified specialist in kidney nutrition to learn what’s best for you.
