Monday, July 15, 2013

The CBC Test Explained

I realized that, after three years of writing this blog, I still haven't gone over the standard Complete Blood Count (CBC) test that some of us get on a weekly basis. Mea Culpa...I should have done this long ago. So here goes:

There are two versions of the CBC test (or possibly more, but I know of two). They are the regular CBC and the CBC w/ Auto Differential. I'll go through the simple CBC in this post. In the next post I will add the extra bits for the CBC w/ Auto Differential. Please know that CBCs may not all be reported identically, so the names/abbreviations are more important than the order.

CBC part 1: tests for things other than your red blood cells:


  1. Platelet: Platelets are the cells in your blood that stop you from continuing to bleed if you cut or bruise yourself. When there is an injury, the platelets rush to the site and try to heal the wound. If you have too few platelets then you are very likely to bruise easily, and cuts won't heal very fast. The normal range is 150-400K. Anything below 10K will normally result in hospitalization. 10-30k is considered dangerous, too. The cut-off range varies from doctor to doctor, but I've found that rheumatologists start worrying when you get to the 30-50K range.
  2. MPV: "Mean Platelet Volume." This shows how big the platelets in your blood are. If you have, for example, a healthy MPV but a low Platelet count, then it i may be that you are making healthy platelets, but then the immune system is killing them. 
  3. WBC: This is your White Blood Cell (WBC) Count. White blood cells are the cells in your blood that protect you from infections (yay!), but can attack your body when you have an autoimmune disease (double boo!)
A Red Blood Cell.
(They don't really have eyes!)
CBC part 2 : Tests that measure something about your Red Blood Cells (RBCs).
  1. RBC: Red Blood Cell [count]; in this case it means the number of Red Blood Cells (RBCs) that are in your blood. RBCs are the cells in the body that absorb oxygen from the air in the lungs, then distribute it to the body. A low RBC count results in anemia. They are the reason that blood that comes into contact with the air is red. The main protein responsible for a RBC's work is...
  2.  Hemoglobin/Haemoglobin: This is a protein that binds to Iron (which we get from our diet or from supplements) and uses it to grab oxygen from the air. If your count is below the average range then you will also be considered anemic, and may have to take Iron supplements.
  3. Hematocrit/Haemotocrit: Hem/Haem (depends which side of the pond you're on) means "blood". Crit means "count." So the word means "blood count"...very helpful, right? Yeah. What hematocrit means in a CBC is the % of your blood that is made up out of RBCs. Your blood should have many different kinds of cells, so if the Hematocrit is below 36% or above 46% then something may be wrong; you might not be making enough RBCs, you might be making too many, or you might be making the right amount, only to have some *$%@ autoimmune disease cause your immune system to kill the cells.
  4. MCV: Technically this is the "Mean corpuscular volume." What this really mean? Well, it can tell you a lot about the size of the Red Blood Cells in your blood. This, in addition to the hematocrit, can tell the doctor a lot about your blood production, and can alert them to any serious problems (like, for example, a whole bunch of teeny tiny immature RBC's) that might be going on with the RBCs themselves. Basically it can tell your doctor that your cells are healthy or unhealthy.
  5. MCH: This stands for "mean corpuscular hemoglobin." This is like the MCV, except that it counts the weight of the hemoglobin in the blood. The normal weight is around 26.0-34.0 picograms. 
  6. MCHC: "Mean Corpuscular Hemoglobin Concentration." This is the same as the above test, except that it's measuring the concentration of hemoglobin within cells instead of the total weight in the blood. Once again, these tests are supposed to alert a physician to a problem with the ratio of hemoglobin either in the blood (MCH) or within RBCs themselves (MCHC). This count can indicate a number of disorders, including sickle cell disease. 
  7. RDW: "Red Cell Distribution width." This tells the doctor how much variation there is in the size of your red blood cells. Normally this variation is 11.5-14.5%. This means that the cells are pretty much the same size. Too much variation might show a problem with your bone marrow.
  8. nRBC: Nucleated Red Blood Cells. This one is kind of technical, but basically  RBCs in the blood don't have something called a nucleous. If your RBCs do have nuclei, then you have, essentially, baby RBCs floating around in your blood. This points to a disease in the bone marrow, where all blood cells are made.

I know, it seems like there are an awful lot of tests that are measuring something or another about Red Blood Cells, but your body will die without oxygen, and only RBCs can bring oxygen from your lungs to the rest of your body. So it's important to know that you have the right number, size and percentage of RBCs in the blood. Since Hemoglobin does all the work in RBCs, it's equally important to make sure that you have the right number, amount and percentage of hemoglobin in your blood.
White Blood Cells:
Both a blessing and a *$%@
nuisance for people with autoimmune diseases!!

Phew. That's it for the "CBC" test. All of the tests measure either how many or how healthy various cells in our blood cells are. In autoimmune diseases like lupus it is not uncommon to have low RBCs, WBCs and Platelet Counts. This is because our stupid immune system keeps killing them.

Sources: Wikipedia, WebMD, Johns Hopkins, others.

My standard disclaimer applies: my blog should never be considered medical advice, or used as a substitute for talking to your physician. (Sorry, folks, my brother is a lawyer, so I always have to throw that bit in). Also, I have brain fog, and I do make mistakes. Please tell me if you catch any!!!!


  1. It is truly a blessing to have blood that just does its job. Thanks for the reminder to count that blessing. And oxygen is very important!!! (I had a horrible cold last week, so I'm enjoying breathing more than usual this week.) However, you do have the cutest red blood cells I've ever seen. I hope that your volume of mean platelets, or any other mean, nasty, or unkind cells for that matter, remains very low.

  2. sam can you do one creatine ra why some swell with pain others have much pain little swelling what causes ankles to swell badly if kidneys are normal how do you no if you need go hospital idea to deal with more then one illness how do you find strength as young woman to deal gastro disorder you have how to no if you possibly have it thx sam for all you do sending great big gental hug sharon

    1. Here you go:

      Please tell me if anything is unclear.

  3. Sam do you want typo's sent to you. There were a few more than usual in this post. Not a complaint, but a simple ask if you want the feedback. I know the fog has been thick for a while. Hoping and praying things improve for you.

  4. Hi. I'm a college graduate (B.S. in Biology) and I would very much love to get into some kind of research that has to do with better treatments and potential cures for Lupus. I do not plan on trying to get into medical school and, to be honest, I'm not really looking to get into a lab where I have to just randomly do whatever the PI is doing. I want to do Lupus research. If it's alright with you, could you please give me a little advice on what direction I should take (how to get started)? I have so many ideas and experiments that I would like to try (more specifically with tregs and a few suspect bacterial infections), but I have no idea where I should even begin. Now, I have about 2 years worth of lab experience ( 3 and 4th year undergrad student worker/lab tech) which isn't much, but I generally understand the basics with funding and such. So I do understand that no matter what, I won't just be able to jump head first into doing what I wish to do. However, right now, I just want to start follow my dream. I honestly believe that one day this disease will be treatable without all of the toxic drugs and unwanted, god awful side effects. I want to help people. Please, please, please. If you can find the time to help me with this, I will be seriously grateful for the rest of my life.

    Thank you for your time,


    P.S. By the way, I suffer from Stage III non-proliferative Lupus Nephritis at the age of 31, so I totally understand how all of these things feel--hence, my drive to make things better for all of us. :)

    1. Where are you located and/or are you willing to relocate for work? I can tell you a few places that are working on lupus research, but I don't know if they're currently hiring; this is a terrible economy for us scientists!

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