If you have Chronic Kidney Disease, you probably get a lot of labwork done, and one piece of that labwork is your Complete Blood Count. Doctors use the Complete Blood Count for a variety of reasons, including to check and see if you may be anemic and get clues as to why. If you want help deciphering your anemia labs, just keep reading!
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What is a complete blood count?
A Complete Blood Count, also called a CBC, is a collection of lab tests that provide information on three different types of cells in your blood:
- Red blood cells – these are the cells that carry oxygen to various parts of your body
- White blood cells – these are the specialized cells that help to fight infections
- Platelets – these cells help your blood clot so that you stop bleeding after getting a cut or scrape
A complete blood count helps alert your doctor if you are starting to develop anemia. Anemia occurs when a person has too few red blood cells. If you have too few red blood cells, your body might not be getting all of the oxygen that it needs to keep things running smoothly.
People with CKD are at an increased risk of developing anemia, because the kidneys play a vital role in the process of making red blood cells.
The kidneys make a hormone called erythropoietin, also called EPO for short. EPO travels to your bone marrow where it tells the bone marrow to make more red blood cells. When the kidneys are damaged, they eventually produce less EPO, which means your bone marrow makes fewer red blood cells. This ultimately leads to anemia. The more advanced kidney disease is, the more likely you are to develop anemia.
Hemoglobin and Hematocrit
Hemoglobin is one of the labs included in a complete blood count. Hemoglobin is a protein inside red blood cells that picks up oxygen. The lower your hemoglobin level, the less oxygen is being carried around to the body, so this is one of the primary labs that is used to diagnose anemia.
Another lab that may be used to determine anemia is the hematocrit. Your hematocrit lab tells you the percentage of your blood that is made up of red blood cells (the rest of the blood is things like plasma, platelets, white blood cells, etc). If your hematocrit is low, you may also be considered anemic.
For women, a hemoglobin less than 11.5g/dl or a hematocrit less than 35% is considered anemia.
For men, a hemoglobin less than 13.5g/dl or a hematocrit less than 40% is considered anemia.
A hemoglobin level less than 10g/dL is considered severe anemia. Severe anemia is associated with the development of left ventricular hypertrophy, heart failure, and progression of kidney disease.
If you have CKD, it is recommended that your doctor monitor your anemia labs at least once a year if you have Stage 3 or twice a year with Stage 4 or 5. If you become anemic, they will want to check these labs every three months to monitor for changes.
Red Blood Cell Count
The red blood cell count (sometimes abbreviated as RBC) measures the number of red blood cells you have in a given amount of blood. This number is not used to diagnose anemia because it can vary for a variety of reasons. This lab could be low if you have anemia or lose a lot of blood. The red blood cell count is also used to calculate the Mean Corpuscular Volume.
Mean Corpuscular Hemoglobin and Mean Corpuscular Hemoglobin Concentration
The mean corpuscular hemoglobin (MCH) and the mean corpuscular hemoglobin concentration (MCHC) both measure how much hemoglobin (the oxygen carrying compound) is found inside a red blood cell. The MCH measures the total amount of hemoglobin inside a red blood cell, while the MCHC measures what percentage of the red blood cell is filled with hemoglobin.
These can sometimes be difficult to distinguish, so I like to use an analogy of water in a glass. If you put 4 ounces of water into a small glass and 4 ounces of water into a large glass, both glasses still have the same amount of water in them. However, if you look at each glass, they will have a different concentration of water. The small glass may be 50% full while the large glass may only be 25% full. The large glass has a lower concentration of water and higher concentration of air.
With red blood cells, you could have the same amount of hemoglobin in a small red blood cell and a large red blood cell (this would be measuring the MCH), but when you look at what percentage of each red blood cell is filled with hemoglobin (this would be the MCHC), the smaller cell will have a higher concentration because it is easier to fill up the small cell, while the large red blood cell may have a lower concentration.
Mean Corpuscular Volume
The mean corpuscular volume, sometimes called the mean cell volume or abbreviated as MCV, is a lab that tells you the average size of your red blood cells.
A normal MCV is between 80 – 100fL. If you are anemic and your MCV is less than 80 fl, your anemia would be described as microcytic anemia. If you are anemic and your MCV is higher than 100, your anemia would be described as macrocytic anemia. If your MCV is within the normal range and you are anemic, we call that normocytic anemia.
When someone is anemic, the MCV is often used as a starting point for troubleshooting what the cause of the anemia may be.
Microcytic anemias can be an indicator of iron deficiency while macrocytic anemia may indicate a deficiency of Vitamin B12 or folic acid, although there are many other causes. You may also have these deficiencies with a normal MCV. A normal MCV does not mean that you don’t have a nutrient deficiency.
If you think you may have a deficiency in any of these nutrients, it is important to work with your healthcare team, including your doctor and dietitian, to determine:
- Whether you are truly deficient
- How you should go about correcting the deficiency (you don’t want to over supplement without proper monitoring, but you also don’t want to under supplement – especially if you have a condition that increases your nutrient needs)
- and (most importantly!) why you have a deficiency in the first place. The cause of the deficiency helps determine the dose of supplement, how to take the supplement, and how to prevent another deficiency since it can be a sign of an underlying condition.
Red Cell Distribution Width
The red cell distribution width, also abbreviated to RDW, measures the variation in the size of the red blood cells. If all of your red blood cells are a similar size, your RDW will be normal (or even low. A low RDW is not bad). If your red blood cells are different sizes, your RDW will be higher.
One way the RDW is often used is to help interpret the mean corpuscular volume, or MCV. If someone has a normal MCV, but they have a high RDW, it could mean that they have some microcytic cells and some macrocytic cells. Your healthcare provider would want to troubleshoot different things depending on whether they think you have normocytic, microcytic, or macrocytic anemia.
Troubleshooting Anemia
If your hemoglobin or hematocrit are low and indicate that you have anemia, your doctor will look at some of the other labs within the Complete Blood Count to determine the next steps. Additional labwork or tests will always be needed to determine the cause of the anemia. It is not possible to determine the cause of anemia just by looking at the Complete Blood Count.
The important thing is that your healthcare team continues to troubleshoot the cause of your anemia. It is not uncommon for some degree of anemia to be blamed on Chronic Kidney Disease and the lack of erythropoietin, however most people with CKD have multiple contributing causes to their anemia. It may not be possible to address the lack of erythropoietin at your level of anemia, but figuring out other contributing causes – and fixing them! – can have a noticeable impact on your labs and, more importantly, how you feel.
If your hemoglobin and hematocrit levels are normal, I would encourage you to keep track of the levels and pay close attention to when they start to fall. Declining hemoglobin – even if it is still technically normal – is an early indicator that something may be off. Catching the problem early can help you avoid the fatigue of anemia.
If you are not already working with a dietitian, I highly recommend doing so because nutrition plays such a big role in anemia. Most insurance companies cover the cost of seeing a dietitian. To see if I accept your insurance and work in your state, please check here for information about appointments. For help finding a renal dietitian in another state, please check out this page on finding a kidney dietitian.
The topic of anemia and how to troubleshoot is a HUGE topic (that I can literally spend hours discussing from a nutrition standpoint). More than I can possibly include in a blog post. To learn more about CKD Anemia and Nutrition, check out the resources below.
If MCV is Normal
If your Hemoglobin or hematocrit are low, and the MCV is normal you’ll want to start with troubleshooting Normocytic anemia. Our Kidney Foodie Academy has a one hour webinar recording covering various causes and contributing factors to normocytic anemias (it’s way more than just a lack of EPO). We discuss the numerous nutritional strategies that can be implemented to help address different causes of normocytic anemias. Note: If your RDW is high, it could mean that you have a mix of microcytic and macrocytic anemia, so you may want to watch all three webinars.
Webinar Recording Link: CKD and Anemia Part 1: Normocytic Anemia
Note: You’ll need to sign up for Kidney Foodie Academy here first: https://kidneyfoodie.com/kidney-foodie-academy/
If MCV is Low
If your MCV is high, you’ll want to start with troubleshooting microcytic anemia. If your MCV is normal, but your RDW is high, you’ll want to view both the microcytic and macrocytic anemia webinars. Our Kidney Foodie Academy has a one hour webinar recording covering various causes and contributing factors to microcytic anemias. We discuss the additional labwork needed to diagnose an iron deficiency, and the numerous nutritional strategies that can be implemented to correct an iron deficiency, troubleshoot side effects from iron replenishment, and help prevent a deficiency in the future.
Webinar Recording Link: CKD and Anemia Part 2: Microcytic Anemia
Note: You’ll need to sign up for Kidney Foodie Academy here first: https://kidneyfoodie.com/kidney-foodie-academy/
If MCV is High
If your MCV is high, you’ll want to start with troubleshooting macrocytic anemia. If your MCV is normal, but your RDW is high, you’ll want to view both the microcytic and macrocytic anemia webinars. Our Kidney Foodie Academy has a 45-minute webinar recording covering various causes and contributing factors to macrocytic anemias. We discuss the various risk factors for macrocytic anemia, additional labwork than can be ordered to diagnose deficiencies, and strategies to help prevent a deficiency in the future.
Webinar Recording Link: CKD and Anemia Part 3: Macrocytic Anemia
Note: You’ll need to sign up for Kidney Foodie Academy here first: https://kidneyfoodie.com/kidney-foodie-academy/