In today’s VETgirl online veterinary continuing education blog, we review the importance of the PCV/TS.

Many people blow off simple quick assessment tests like the packed cell volume (PCV), total protein (TP), blood glucose (BG) and AZO (BUN). However, these $5 diagnostic tests can provide so much information, particularly in the veterinary emergency room or ICU! [For more information on the difference between TP (total protein) and TS (total solids), check out our previous blog post.]

The PCV measures the percentage of red blood cells (RBC) to the total blood volume.  This value is obtained when a blood sample is placed into a small hematocrit tube.

Following hematocrit tube filling, the tube is sealed with clay and placed in the centrifuge for approximately 3 minutes (for most standard 10,000-12,000 RPM centrifuges).  Following centrifugation, the RBCs are separated from the plasma.  Plasma is mostly comprised of water, proteins, glucose, clotting factors, and mineral ions.
When assessing the PCV and TP, it’s important to evaluate these two parameters together. When evaluating the PCV, the first step is to decide if the value is normal.  While the results may vary slightly based on age and species,  normal PCV is approximately 35% – 45%.  While polycythemia (a disease state where the proportion of blood volume that is occupied by red blood cells increases) is possible, most commonly, an increase in PCV is seen with dehydration (commonly termed hemoconcentration). A more common clinical problem – at least in the veterinary ER or ICU – is the dilemna of determining why the patient is anemic (e.g., low PCV).

This is where evaluating the PCV in relation to the TP is handy!

The TP is measured by breaking the hematocrit tubes (once the PCV is determined) following centrifugation, and placing the plasma directly onto the refractometer.  The refractometer is then assessed (pointing it into the direction of light) – check out the picture to see the reading. The TP is the number read directly from the  visible scale (in this picture, a total protein of approximately 1.6). Next, the color and clarify of the plasma should be assessed. If the plasma has a yellow-tinge, it typically represents an increase in bilirubin level. If the plasma has a red-wine color, the sample is typically hemolyzed (e.g., either due to traumatic venipuncture or direct hemolysis within the body, etc.). Lastly, the serum should be evaluated for the presence of hyperlipidemia (e.g., cloudy white plasma) or the presence of a large buffy coat (e.g., a thick, opaque white line found directly above the layer of RBC and plasma); this is typically due to presence of an elevated white blood cell count.

Blog - PCV-TP-Buffy Coat
Similar to the PCV, the TP may vary slightly based on age and species, with normal values ranging from 6.5 – 8.0 gm/dl.  Elevated TP is most commonly seen with dehydration, with less common causes being chronic inflammation, neoplasia, infectious disease (e.g., FIP), or multiple myeloma.  A lower than normal protein level can be seen with hemorrhage, malabsorption, liver disease (e.g., lack of production of albumin), gastrointestinal disease (e.g., protein-losing enteropathy), or kidney disease (e.g., protein-losing nephropathy).

This chart created by Dr. Justine Lee, DACVECC, DABT is an example of how different combinations of PCV/TS can help narrow down disease quickly.


(e.g.,  25%/7g/dL)

(e.g., 25%/70 g/L)


(e.g., 65%/7 g/dL)

(e.g., 65%/70 g/L)


(e.g., 40%/5 g/dL)

(e.g., 40%/50 g/L)


(e.g., 40%/9 g/dL)

(e.g., 40%/90 g/L)


(e.g., 66%/8 g/dL)

(e.g., 66%/80 g/L)

↓ PCV/ ↓ TS

(e.g., 25%/5 g/dL)

(e.g., 25%/50g/L)


Hemolytic anemia Polycythemia vera Protein-losing enteropathy (PLE) Multiple myeloma Hemoconcentration Chronic blood loss (e.g., melena)
Aplastic anemia Hyperthyroidism Protein-losing nephropathy (PLN) Feline infectious peritonitis (FIP) Blood loss (e.g., subacute)
Pure red blood cell aplasia Hyperadrenocorticism Liver failure (lack of production of albumin) Chronic globulin stimulation (i.e., dental, skin disease)
Anemia of chronic disease Hemorrhagic gastroenteritis (HGE) Acute blood loss (with splenic contraction) Severe dehydration + anemia (e.g., CRF)
Is the sample hemolyzed? Icteric? IMHA EPO-producing tumor (renal) Third spacing Lipemic serum
*Copyright VETgirl, LLC.

    • Not at all – there’s no good blood work parameter we look at for “shock”. Maybe lactate for perfusion, but normal PCV/TS can still exist with shock. Look at the patient for clinical signs instead.

  1. We just heard about this PCV number for the first time, regarding our West Highland Terrier. She has had problems most of her life with her main problem being Addison’s Disease.
    Over the past year or two, digestion problems have been at the top of the list. Explosive problems. When she reacts to an episode by trembling and excessive panting, we panic and take her to the doctor. Her most recent episode occurred after vet hours and we took her to a local 24 hour emergency pet hospital. After poking and prodding as usual, one of the reports we received was that she was dehydrated and her PCV was at “57, and we like to have it below 50”. That is what and how we were told.
    Any comments?
    So… we’re trying to educate ourselves to what this means and if we can help it!

    • An elevated PCV is typically seen with hemoconcentration or dehydration. As your dog has Addison’s disease, she is more at risk for “shock” and hemoconcentration. When in doubt, talk to your vet about dosing her with more prednisone when she has “stressful” days (e.g., going to the groomer, going to the dog park, etc.). Good luck!

  2. PCV is 38% and his TP is 7.5 g/dl.
    So if you only have the PCV & TP values how do you figure out the MCV, MCH, MCHC

  3. Is there any differences between the PCV of 2-year old racehorse in training and 4-year-old racehorse runners? Thank you in advance.

  4. In an emergency situation, when a vet does a CBC test, is this separate test still necessary?

  5. In my case they did a comprehensive diagnostic analysis + CBC and apparently also a separate PCV & TP text. Is the latter redundant?

  6. Hi Marcia, I’m a vet nurse at an emergency clinic. You have a great question about CBC and a PCV/TP test. A CBC (complete blood count) gives you hydration status, anemia status, signs of infection, blood clotting ability and immune system response. It does have a portion that reads “HCT” which would be the % of red blood cells (determining anemia & hydration status). That part of the test is equivalent to the “PCV” percentage you would get with our PCV/TP test. There are two reasons I can think of that would make a PCV test still necessary in some cases. A CBC machine is not always available, however a PCV can be used in a centrifuge and assessed manually. The centrifuge separates the blood into sections and we vet tech’s will read exact measurements of: the serum color (abnormal color here can indicate liver disease in some cases), the % of white blood cells (large amount indicates an infection), and of course the PCV %. This test also includes the TP or T/S, that reading is important because it gives you a more specific measurement of the issue. A high reading on the TP or T/S can suggest dehydration, inflammation, or an infectious disease. A low reading can indicate hemorrhage, malabsorption, liver disease, gastrointestinal disease, or kidney disease. A CBC test will only tell you the PCV or HCT reading, a PCV test will give you more specific data on the hydration and anemic status. Your Vet may request additional tests to have clear understanding of your pet’s health status as each blood test has a different focus. Hope this helps.

  7. If you are provided fluid therapy and the PCV% decreases (as expected). What would be a reason for TP to increase instead of also decrease?

  8. If you’re struggling to get an adequate sample off a patient with bad veins or peripheral edema, is it appropriate to suck the sample straight from the syringe to the hematocrit tube without first placing it in a tube with anticoagulant? If done immediately? Ive read that washing a syringe with heparin supposedly doesn’t yield accurate results with alligator blood. I feel terrible trying and failing to get enough blood from hospitalized patients to fill a blood tube when all I need is a smidgen for the crit tube but I desire accuracy and avoiding unnecessary transfusions or decisions based off flawed results.

  9. If you have/can get the mini collect EDTA you can draw with a 1 cc syringe and put it in there so it doesn’t clot as you prepare the samples and it leaves you enough where you’ll have extra if needed to respin! I find it gives more control less worry on blood clotting in syringe+don’t need to draw so much blood in the first place! I haven’t used a heparinized tube to collect in these cases so I can’t speak on it’s accuracy with alligators but I know EDTA is preferred on a general bases so maybe this can help?

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