March 2, 2023

Hematology For Pet Owners: A Comprehensive Guide

Definition of Hematology

Hematology is a branch of medicine involving the study of blood and the treatment of its diseases. Blood cells form and mature primarily in bone marrow, which is the tissue found within the cavities of bones. As it circulates throughout the body, blood performs a number of crucial functions. It transfers oxygen and essential nutrients (including vitamins, minerals, fats, and sugars) to the tissues. It transports carbon dioxide to the lungs, where it is exhaled, and waste products to the kidneys and liver, where they are eliminated. It delivers hormones, chemical messengers, to different body parts, enabling these parts to communicate with one another. Furthermore, blood contains cells that fight infection and prevent bleeding.
There are three cellular elements in blood: red blood cells, white blood cells, and platelets. Basically, red blood cells supply the body with oxygen, white blood cells protect against infection, and platelets start the formation of blood clots.
Hemoglobin serves as the respiratory pigment in human blood, whereas animal blood may also contain other types of respiratory pigments. This is the primary distinction between human and animal blood. Different types of blood have different colors depending on the type of respiratory pigment that is present in them.
Red blood cells in all animals contain A and B antigens. Other antigens may also be present in animals like dogs, cats, and horses, as well as cattle. The two types of blood grouping systems that can be found in monkeys and apes are human-type and simian-type. These animals’ blood grouping systems are distinctive. The most accurate way to distinguish between mammal blood types is through DNA testing.
Blood disorders are quite diverse. They can occur as normal responses to abnormal circumstances, such as an increase in white blood cells in response to an infection or disease. They may also occur as primary blood abnormalities, such as a deficiency of all blood cellular elements due to bone marrow failure. Moreover, abnormalities may be quantitative (excess or deficiency of cells) or qualitative (abnormalities in the way cells function).
In this article, we will tackle the most common blood diseases that your veterinarian might encounter. These diseases can be very diverse, but understanding them can help you take better care of your dog or cat.

Common Blood Diseases and Conditions in Small Animals

A. Anemia

Red blood cell count decline is referred to as anemia. The body’s tissues receive oxygen and nutrients from red blood cells. Before being taken out of circulation and replaced with newly synthesized red blood cells from the bone marrow, these cells circulate for roughly 70 to 80 days. Anemia can quickly deteriorate into a serious or even fatal condition since cells won’t receive enough oxygen or nutrients to survive without enough red blood cells in circulation.
Lethargy is frequently the first indicator of anemia because it deprives the body of oxygen, which serves as the body’s fuel. The energy level of an anemic cat may be low, and it may also sleep more than usual. Due to red blood cell breakdown, the cats’ or dogs’ gums may appear virtually white or even yellow (jaundice). In severe cases, cats or dogs may experience breathing difficulties, and respiratory and heart rates may rise as the body tries to make up for the red blood cells’ reduced ability to carry oxygen throughout the body. Fever and loss of appetite may be brought on by an infection or an inflammatory reaction, depending on the source of the anemia. Blood loss in the stomach or intestines can result in black feces, and the destruction of red blood cells might be indicated by darkened urine. However, the symptoms of anemia can be difficult to recognize, and if a cat or a dog has had anemia for a long time, their body has probably had time to make up for it, so it may not exhibit any symptoms when they are at home.
Anemia can occur in your dog or cat for a variety of reasons. The following are a few of the most typical causes of canine anemia:

  • Chronic diseases that suppress red blood cell production
  • Cushing’s disease
  • Infectious diseases (including canine distemper and feline leukemia virus, for example)
  • Bleeding from the intestines
  • Medications that interfere with the production of red blood cells
  • Severe blood loss due to injury or accident
  • Blood loss caused by parasites
  • Poisons or toxins
  • Cancer
  • Tick-borne diseases such as Lyme disease
  • Poor nutrition
  • Bone marrow disease
  • Kidney disease
  • Hypothyroidism 

B. Blood Clotting Disorders

When bleeding occurs in an organ or body part, a process is set in motion to stop the bleeding. This is called hemostasis. To work, hemostasis requires an adequate number of platelets, the right amount of blood clotting proteins (often referred to as factors), and blood vessels that constrict properly. The blood vessel wall cracks as a result of trauma (injury). The blood vessel responds by constricting, causing blood to flow more slowly, and starting the clotting process. Platelets rush to the shattered wall, where certain proteins alter their round shape into a spiny one. Fibrin is a long protein strand formed by other proteins. These fibrin strands create a net that captures platelets and blood cells and aids in holding them together to form a clot that closes the hole in the vessel wall. Other proteins finally interrupt the clotting process and disintegrate the clot once it has formed and stabilized.

Bleeding problems can be congenitally present at birth or develop later in life. Blood clotting protein deficiencies commonly manifest as hematoma formation, joints bleeding into body cavities, and delayed bleeding and bruising deep in tissues (a pocket of blood that forms outside of a blood vessel). The most common symptoms of platelet abnormalities are minor surface bruises, nosebleeds, black stools from internal bleeding, and prolonged bleeding at injection and surgical sites.

Animals can clot excessively as well. These conditions, often known as “hypercoagulable states,” can cause arteries to become clogged. They may be acquired or result from inherited anticlotting protein abnormalities. Animals are more likely to develop acquired clotting diseases than hereditary ones.

Bleeding disorders include clotting protein disorders, platelet disorders, and vascular disorders.

Diagnostic Testing

Blood tests aid your veterinarian in reliably, safely, and efficiently identifying the origins of sickness and keeping track of the development of medical disorders and treatments. This explanation of typical test results may help you understand your pet’s health and how to take care of it.

A. Complete Blood Count

Blood test results require a well-informed and coordinated team effort for investigation and treatment. The most likely type of blood test that your veterinarian will order is a complete blood count, also called a CBC. A complete blood count (CBC) is a blood test used to measure and evaluate cells that circulate in the blood. A CBC can be used to check for infections, anemia, and other illnesses. In some cases, the results of the CBC will prompt your veterinarian to recommend other diagnostic tests.
When the early CBC tests started in the 1950s, laboratory technicians counted each individual blood cell under a microscope. As medical and technological advancements continue, a newer generation of diagnostic tools known as 5-part differential is becoming available in clinics. These devices provide accurate and reliable results in a matter of minutes. A 5-part cell counter can differentiate all types of WBC (white blood cells) (lymphocytes, monocytes, neutrophils, eosinophils, and basophils). 5-part analyzers provide in-depth information about the sample.
The CBC includes multiple abbreviations and names. To make it easy, the following can help guide you through the results that your veterinarian will explain:
WBC is an abbreviation for “white blood cell count”. These cells help fight infection and respond when an area of the body becomes inflamed. Elevated white blood cell counts indicate infection, inflammation, and some forms of cancer or leukemia.
RBC is an abbreviation for “red blood cell count”. These cells are responsible for transporting oxygen throughout the body. Oxygen is used as fuel for the body and is very important. Low red blood cell counts are referred to as anemia and can be a result of blood loss, active bleeding, bone marrow disease, or excessive red blood cell breakdown that is seen in some immune diseases and toxin ingestion.
HGB is an abbreviation for “hemoglobin”. This molecule is in charge of binding to and releasing oxygen from red blood cells. Without hemoglobin, oxygen cannot be transported.
HCT is an abbreviation for “hematocrit”. The hematocrit is a calculated percentage of red blood cells in the circulation.
MCV is an abbreviation for mean corpuscular volume. This is the average size of the red blood cells. A high MCV usually indicates certain vitamin deficiencies. A low MCV indicated an iron deficiency.
MCH is an abbreviation for mean corpuscular hemoglobin. This is the average weight of hemoglobin in each red blood cell and is different from the hemoglobin circulating in the blood. A high MCH indicates poorly oxygenated blood. A low MCH indicates an iron deficiency.
MCHC is an abbreviation for mean corpuscular hemoglobin concentration. This is the average percentage of hemoglobin in each red blood cell.
PLT is an abbreviation for platelets. The platelets are responsible for sealing any leaks in the blood vessels.

B. Blood Smear

A blood smear is where you put a drop of blood on a microscope, allowing your veterinarian or lab technician to look under the microscope for abnormalities. Examination of blood smears is an integral part of hemological testing. Blood smears are useful for examining cell morphology and identifying blood-borne parasites.

C. Coagulation

The series of actions that cause a clot to form is known as coagulation. The body uses coagulation to stop bleeding after any damage to a blood vessel or tissue. Blood components called platelets play a role in the development of platelet “plugs” at the site of a blood vessel injury. Other components are involved in the clotting process, making it essential to test for other indicators as well.
Coagulation tests may be undertaken for a variety of reasons. Dog coagulation tests may be used for “screening purposes” prior to diagnostic or surgical procedures in breeds known to have a higher incidence of clotting factor deficiencies. In other cases, animals can experience unidentified bleeding episodes, and the clotting function needs to be assessed. Because the liver makes coagulation factors, severe liver disease can make it hard for the blood to clot. Animals with liver problems should also be tested regularly.
Your veterinarian will inform you about the coagulation tests required. Affordable testing solutions like the partial thromboplastin time (PTT) and activated partial thromboplastin time (aPTT) are screening tests that help evaluate your pet’s ability to appropriately form blood clots and can be done in the clinic with minimal hassle.

Treatment Options

A. Medication

Your veterinarian will determine the best course of action to help your pet recover if it has been diagnosed with a disorder. Remember, you are the animal caretaker, and your pet is a part of your family. It is important to listen to all the recommendations of your veterinarian.

The veterinarian might prescribe a diet, medication, or other supplements to help your pet recover. Make sure to take notes on your veterinarian’s advice on the administration of medicine. Don’t be reluctant to ask questions, and don’t let things go over your head. Make sure to understand what is needed for your pet’s health.

If a medication is prescribed daily, make sure to use your smartphone to notify you when to administer the medication.

If your pet underwent surgery or was hospitalized, make sure you have a detailed discharge instructions for their care at home. 

A. Blood Transfusions

Sometimes your veterinarian might request a blood transfusion. A blood transfusion is when your pet receives blood from a donor or a blood bank. It’s a very safe procedure that can be lifesaving.

Need for blood transfusions are sometimes used in the treatment of acute or chronic anemias. Animals with bleeding problems might need whole blood, red blood cells, plasma, or platelets more than once.


A. Vaccinations

Vaccines are a crucial part of the preventative health care offered to veterinary patients and can benefit dogs and cats by lessening the morbidity and mortality associated with the infectious agents the vaccines were designed to prevent. For example, canine distemper virus and canine parvovirus are common killers of puppies.

Feline leukemia virus (FeLV) is a virus that infects only cats. It depresses the immune system, and cats tend to remain infected for life. FeLV is an important cause of anemia in cats and can cause several types of cancer. It is found worldwide and is transmitted through the exchange of bodily fluids (such as from a bite), but it can also be transmitted from mother to kitten.

Your veterinarian will determine the vaccines required by your pet. For vaccinated animals, an immunologic testing (also known as Rapid Tests) has to be done to determine the vaccination status of the pet or if the need of any additional dose. 

B. Early Detection

Although your pet may appear well, the natural instinct of animals is to disguise or hide any outward appearance of illness. This behavior has obvious advantages in the wild, but it can be harmful, if not fatal, in domestic companion animals. A regular wellness exam can ensure this happens. It’s important to identify the early signs of illness in order to begin treatment or take measures to prevent further damage or further progression of a disease.

Remember that animals age at an accelerated rate compared to people. It is recommended that your pet receive an annual wellness exam; some pets, for example, older pets, may need exams twice a year. Your veterinarian may also recommend a wellness exam before a surgical procedure (spay / neuter, dental cleaning, etc.).


In most instances, vets recommend that all pets have yearly bloodwork as a very useful part of any animal’s preventative care. Even if your pet seems perfectly healthy, test results can be tracked every time to help your vet to identify any developing patterns that could suggest that an illness or health problem is developing. At this stage, it could be possible that something can be done to prevent disease or disorder from occurring.


Siegel, A., & Walton, R. M. (2020, May 29). Hematology and Biochemistry of Small Mammals. PubMed Central (PMC).

WHITBREAD. (2022). Clinical Hematology – Clinical Pathology and Procedures – MSD Veterinary Manual. MSD Veterinary Manual.

Anemia. (2017, October 9). Cornell University College of Veterinary Medicine.

Cotter. (2022, October). Bleeding Disorders of Cats – Cat Owners – MSD Veterinary Manual. MSD Veterinary Manual.

Chhabra, G. (2018, March). Automated hematology analyzers: Recent trends and applications. PubMed Central (PMC).

Pellenz. (2017). What is Flow Cytometry (FACS Analysis)? | What Is Flow Cytometry (FACS Analysis)?

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