Lab Values Every Nursing School Student Needs (Critical Thinking Method)

If you're just memorizing lab values, the hard truth is you won't be ready for your nursing exams. Now, the key is, is to start critically thinking about it. So in this video today, we're going to fix that, and I'm going to walk you through the key critical thinking points for the lab values that are almost guaranteed to show up on your nursing school exams so that you can pass. Let's dive in. So the biggest thing for you to know when it comes to lab values is that your exams and the NCLEX are not going to be testing you on whether you can memorize the number or not. Here's what they're testing you on: they're testing you on whether you know what to do when that number is either high or low. So we're not just memorizing here, my friend. For every lab value, we're going to ask 2 main questions: What does this lab value measure? And what does the body do when this lab value is off, so it's either too high or too low? This is how you're going to stop memorizing lab values and actually start understanding them and critically thinking through them. Let's start with the complete blood count, aka the CBC, and there are 3 big players here that you've got to know about. First up, we have white blood cells, or the WBCs. Now a normal white blood cell count is about 4,500 to 11,000 cells per microliter of blood. But as with most lab values, these numbers can vary based on the lab or facility that's testing it, So you want to be sure to check with your nursing program just so that you're learning the ranges that they want you to learn, because there can be some variation with these. So you can think of white blood cells as the body's army. Now, the white blood cells are sent out when there's an infection in the body or inflammation happening. So a high WBC count, it tells us the body is fighting off something. But here's a big critical thinking point for you that we need to talk about, okay? A low White blood cell count can also be a problem because it means that the patient barely has that army left to fight with, right? So a low WBC can indicate that the patient is immunocompromised. And what do we need to do for a patient who is immunocompromised? You should be thinking about infection control precautions, okay? Things like not sharing personal items like towels, they should be wearing a mask when they go out, washing their hands frequently, things like that to help reduce the chances of that patient getting sick. Since they don't have that white blood cell count, that high WBC count, to help fight off infections, they're more likely to get sick. So do you see how when you know what the white blood cells do, that you can realize then that that number is low, and then it drives those nursing actions that you need to do? Okay, that's the critical thinking piece that is so, so important in nursing school. Now next up is the hemoglobin and the hematocrit. This is also called the H&H, and these two, they go together, they're BFFs. The hemoglobin is the spot on the red blood cell that carries the oxygen molecule, and there's a bunch of them on every red blood cell. Now, a normal hemoglobin is around 12 to 17.5 grams per deciliter. And the hematocrit also has to do with those red blood cells. Now, this one tells you how many red blood cells there are in relation to the total blood volume. Volume. So this one is actually a percentage. A normal hematocrit level is around 37-47% for females and 42-52% for males, but again, this range can vary based on the standards of the lab that's testing it, so definitely check with your program. Now both of these can be low for several reasons. You're looking at things like trauma, blood loss, infection, or a decrease in kidney function, and they're really measuring how well the blood can carry oxygen around the body. So when you see a low H&H, connect it back to that patho, okay? Less oxygen-carrying capacity means a patient who is tired, pale, short of breath, maybe dizzy, simply because the body isn't getting enough oxygen to help those organs function properly. Now our third CBC player here is platelets. Now I know I glumped H&H together because they kind of go together, but we'll call platelets III. And a normal platelet count is about 150,000 to 450,000 platelets per microliter of blood. Now, platelets are the clotting cells. They are the ones that clump together and clot the blood. So if there's more platelets, the body has more ability to clot. But when there's less platelets, the body isn't able to clot the blood as easily. So let's critically think through this one, okay? If a patient has a low platelet count, What are you going to be more worried about? If you thought bleeding, you are absolutely correct, my friend, because the patient can't form a clot as easily. So then you're looking at bleeding precautions, things like using a soft toothbrush, using an electric razor, gentle handling with that patient, and then watching for petechiae or bruising. So if you see that low platelet count on your exam, Think bleeding precautions. Now, so far the CBC gave us those 3 must-knows. We've got the white blood cells for infection and immune status, we've got hemoglobin and hematocrit for oxygen and anemia, and then we've got platelets for clotting and bleeding. And notice that we didn't just memorize that list of lab values, right, and the ranges, but we're asking what those lab values measure and what the body does if it's too high or too low. Okay, so this is the critical thinking, my friend. So let's keep that going because next up we've got our kidney labs. These are so important. These two are directly related to the kidneys and they go hand in hand: creatinine and BUN. So let's start with creatinine. Creatinine is one of those waste products that the kidneys are responsible for getting rid of and excreting from the body. Now, a core function of the kidneys is to filter the blood and remove waste from the body. So all throughout the day, muscle cells are building up and breaking down, and building up and breaking down, and creatinine is a byproduct of that natural muscle breakdown. So as it's released, it travels through the blood to the kidneys to be filtered out into the urine. Now a normal creatinine level is between 0.6 and 1.2 milligrams per deciliter. Now here's your critical thinking point for this one, my friend. What do you think will happen to the creatinine level when the kidneys are damaged? Is it going to go up or down? Well, it's going to go up, right? Because the kidneys can't filter that creatinine out as well, and more and more is going to build up into the blood. So if you see creatinine higher than normal, your brain should go, hmm, something might be going on with the kidneys. Now the next one is BUN, which stands for blood urea nitrogen. Now there's— this is another waste product that the kidneys filter out. This is called urea, and urea nitrogen is made by the liver as protein is broken down in the body. The liver then sends it into the blood to be filtered out by the kidneys. A normal BUN is between 7 and 20 milligrams per deciliter. So let's practice that critical thinking again: what happens to the BUN if the kidneys are damaged? It increases, right? It builds up in the blood instead of being excreted out into the urine. Increased BUN can also be caused by the kidneys not getting not getting enough blood flow from things like heart failure or dehydration. So if you see a BUN that's increased, you'll want to be thinking about the kidneys. And next up is the electrolytes, and these are huge for your exams. I don't want you to forget these, so I actually made you a quick review lab values cheat sheet to help you remember all of this for your nursing school exams. So just comment the word LABS down below, and I'll send it right over to you so that way you'll have it handy. As you are studying. So electrolytes are a big deal, and you have to know a lot about them to pass your exams. Now, the first one you absolutely must know is potassium, and this is probably the most important electrolyte that you've got to worry about, and it's going to show up a lot on your exam questions. At least it did for me when I was in nursing school. Potassium is a huge one. Potassium has a relatively narrow normal range, and it go— when it goes out of that range, bad can happen very quickly. So normal potassium is between 3.5 and 5 milliequivalents per liter, and potassium does two really big things, okay? It helps with muscle contraction and it keeps the heart pumping. Now, it has a huge effect on the heart, so any shift in potassium in either direction should make you think about cardiac symptoms, okay? So if you have a patient who's at risk for potassium imbalances, like if they're taking diuretics or they have some fluid imbalances, or they have kidney issues, then you'll want to be watching their cardiac conduction on an ECG. So think potassium. And here's a big thing to know about potassium: both ends can be dangerous. Like we said, too high and too low can throw your patient into a cardiac arrhythmia. So potassium is a really important lab value to monitor. And then next up, we have sodium. A normal sodium level is 135-145 milliequivalents per liter. Sodium is super important for helping the muscles contract. Altered sodium levels can cause neurological, neuromuscular, and cardiac changes as well. And sodium can cause fluid shifts too, because wherever sodium goes, water likes to follow. So with abnormal sodium levels, you're watching for things like neurological changes like confusion or seizures. And then the next electrolyte you've got to know is calcium. This is a big one. A normal calcium level is between 8.5 to 10.5 milligrams per deciliter. Now calcium, like you know, it helps with bones, but it also helps with blood clotting, muscle and nerve firing. And there's two major signs that you've got to know for calcium, okay? Trousseau's sign and Wostick's signs, which are twitchy cramping muscle responses that will show up when calcium is low. So we're talking hypocalcemia. You can picture the muscles getting cramped and irritable when calcium drops. Now, this makes sense because calcium is super important for muscle and nerve function. So when it's low, the muscles and the nerves are actually going to be too excitable. So that's why you'll see that twitchiness and that cramping. Now, I walk through all of this in way more depth inside our fluid and electrolyte section inside the Nursing SOS membership community. So if you want critical thinking key points for these fluids and electrolyte imbalances, and all of the other disorders that you've got to know about in med-surg and fundamentals in nursing school, then be sure to check out the NMC. You'll get all of my step-by-step videos, study guides, cheat sheets, all of the things to help you pass your exams in nursing school. You're gonna love it. I'll put the link to all the details in the description below. Now, the next big one is blood glucose, okay? A normal fasting blood glucose is between 70 and 99 milligrams per deciliter. Now, the cells in the body depend on glucose for energy, right? So if there's too little glucose in the blood, then they can't function as well. And if the glucose is high, the body can't use it all, and it just hangs out in the blood. It just kind of floats around, leading to hyperglycemia. And that can cause things like ketoacidosis and damage to the heart, the kidneys, and the nerves. And here's a memory trick to help you out with this: cold and clammy, give me candy. Hot and dry, my sugar is high. So cold and clammy, give me candy— that's the low sugar, okay? And then hot and dry, my sugar's high. So let's critically think through this one. If your patient is cool and shaky and sweaty, you're going to be thinking hypoglycemia, right? And we need to increase their sugar. But if your patient is warm and dry, You'll be thinking high sugar and you'll need to lower it. And of course, we can't forget the hemoglobin A1c, or the HbA1c. Here's why I love this one. The regular blood glucose test gives us a quick kind of snapshot of blood sugar levels in that exact moment, okay? But the A1c is like a quarterly report card. It shows the average blood sugar level over about the last 3 months. So a patient can have a great number this morning but if their A1C is high, you know that they've actually been running high for months. So it's really nice to have that kind of look back. Now, a normal A1C is usually under 5.7%. Prediabetes is 5.7% to 6.4%, and diabetes is above 6.5%. Now let's talk liver labs, and these are super important, and they can easily get skipped when you're studying or mixed up. But remember, I have that free lab values cheat sheet with all of this broken broken down for you, just comment the word "labs" down below and I'm gonna send that right over to you. So you can think of the liver as your body's detox and protein factory, so these tell you how well it's functioning. So first up, we have ALT, which stands for alanine aminotransferase. Now don't worry, that's a big word. Just know that ALT is an enzyme that's found mostly in the liver and it's one of our best ways to check on liver health. Okay, so you'll see it on liver function tests and on the CMP, the Comprehensive Metabolic Panel. Now, a normal ALT is roughly around 7 to 55 units per liter. Now, here's the easiest way to picture this: when the liver is unhappy, whether that's from things like a disease or injury, it's going to throw that ALT out into the bloodstream. I want you to think of this as a toddler having a tantrum. So when the liver is angry about something, really angry, it throws that ALT into the blood. Has a big temper tantrum. So normally, there's just a little bit floating around, but if that ALT is high, the liver is angry, and we need to find out why. So this could be caused by things like hepatitis, mono, cirrhosis, or a fatty liver. Those can all do it. Now here's your key point though: one lab alone doesn't diagnose anything. We can't go off of that. ALT is just one piece of the puzzle that points us toward the liver, but there's other lab values that we have to consider. So next up, we have AST, aspartate aminotransferase. Now this one sounds a lot like ALT, doesn't it? This one is also an enzyme that tells us about liver health, but there's one big difference here. AST is found in other parts of the body, like the heart, pancreas, and skeletal muscles. So here's a memory trick that I love: so you can keep these two straight. The L in ALT tells you that it's mostly the liver, okay? And then S in AST reminds you that it also measures in places like the skeletal muscle. So ALT, liver, AST, skeletal and other places. Now, a normal AST is roughly 8 to 48 units per liter, and it usually gets drawn right alongside that ALT. So let's do some critical thinking around this to really make sure you've got this down. If both are up, the liver is your prime suspect. But if AST is up and ALT is totally normal, hmm, now you're thinking, maybe this is coming from somewhere else, like the muscles, right? So it's really important to know what ALT and AST both are, where they're located, and what makes them increase. Now another huge one is bilirubin. Bilirubin is a red-orange compound, and it's a byproduct of red blood cells breaking down. So this is really important, okay? Red blood cells only live about 120 days, and when they break down, this process makes bilirubin. A normal total bilirubin is roughly 0.2 to 1.2 milligrams per deciliter. And notice that this is not zero, right? Because the body is always breaking down old red blood cells. That's just normal life. So there's always going to be a little bit of that floating around. So here's a critical thinking question for you: if we are constantly making bilirubin, then why isn't everybody walking around just yellow and jaundiced all the time? So go ahead, let's think about it for a second. Well, it's because a healthy liver clears it out for us. The liver excretes that bilirubin and it keeps everything in balance. So then what happens if the liver is not healthy and can't clear it? Well, you've got it, my friend, bilirubin builds up in the blood, and that's when you see jaundice, which is that yellow tint to the skin and the eyes. So anything that stresses the liver, like heavy alcohol use, hepatitis, and new medication, it can lower its ability to clear bilirubin out, and it can lead to jaundice. Now the other side of lab values and electrolytes is IV fluids. Fluids, and you'll be tested on these a lot in nursing school. So click on this video here next, and I'm going to give you a simple breakdown of the types of IV fluids that you've got to know for your exams. And if this video helped you out, hit that like button, be sure to subscribe and click the bell so you never miss a video, and as always, my friend, go become the nurse that God created only you to be. And I will see you over there in that next video.