Creatinine (Cr) Lab Values

In this lesson we’re going to take a look at creatinine.

Creatinine, like BUN, is one of those lab values that we’re going to look at to assess how well are patient’s kidneys are.

The normal lab value for creatinine is 0.7 to 1.4 milligrams per deciliter.

As we use our muscles, there’s this breakdown of all these waste products. One of those things that we look like is something called phosphocreatine, and it’s essentially converted to creatinine. Once muscle breakdown occurs, creatinine is released into the bloodstream, and it’s picked up by the kidneys, and kicked out as urine.

The difference between creatinine and Bun, when we’re looking at kidney values, is it creatinine is more specific to the kidneys because it’s less influenced by diet and hydration.

Just like BUN, this is going to be included in your Chemistry panel and renal panels, so you’re going to submit this in a green top tube.

Now there’s this other test that talks about creatinine called creatinine clearance. And what happens is it compares the level of creatinine in the blood to the amount of creatinine that’s in the urine. The important thing that you need to know about this test is that it is a 24 hour urine sample. So the specifics of this are, that you allow a patient to void, and then you start taking every urine sample for 24 hours after that first sample. So you discard the first sample, and then start collecting urine. There’s usually going to be a big orange container, and you’re going to make sure that that stays on ice. Once that’s all collected you’re going to send that down to the lab. Check with your facility about policies regarding 24-hour urine collection, but the thing that you need to know is that you always discard the first urine sample.

Let’s take a look at some abnormal creatinine values.

If your patient has elevated creatinine on their labs, you can expect some sort of renal disease. The goal of any renal disease is to find out the cause of the kidney dysfunction and then treat the cause first. So if it’s hypertension or toxicity, it’s important to treat those issues first so that the kidneys don’t get further damaged. This is done with medication, lifestyle, and even dialysis.

Another time you’ll see elevated creatinine is on something called rhabdomyolysis. Essentially what happens is that there’s some significant trauma or muscle breakdown that results in release of proteins that damage the kidneys. You’ll also see elevated creatinine on congestive heart failure, in shock, and in some cases of dehydration.

Examples of decreased creatinine, are when you have a loss of muscle mass or something like muscular dystrophy. You also see it in decreased protein intake, liver disease, and also in cases of pregnancy.

When we are looking at our nursing concepts for creatinine, we looking at lab values and elimination since we’re focused on the kidneys.
So let’s recap.

Normal values for creatinine are at 0.7 to 1.4 milligrams per deciliter.

Creatinine is an evaluator for the kidneys, because the kidneys filter out creatinine, and creatinine is more specific to kidneys because it’s less influenced by diet and hydration levels.

You’ll see increased creatinine levels if you have a kidney or muscle damage.

And you’ll see decreased creatinine levels if you have a patient who has a liver problem or muscle wasting.

Lastly, this is an essential renal value, just like the BUN. It’s specific to kidney function and is always going to be included in your kidney labs.

That’s it for this lesson on creatinine. Make sure you check out all the resources attached to this lesson. Now, go out and be your best selves today. And, as always, happy nursing!!