Your vet just handed you a CBC report. There are numbers on it, arrows pointing up and down, and terms you have never seen before. One line reads "neutrophils: HIGH." Another reads "lymphocytes: LOW."

You nod, but you are thinking: what does any of this actually mean? Is my dog sick? How sick? What do we do next?

This guide explains what white blood cells do, what goes wrong when their numbers are off, and when a CBC result should make you drop everything and go to the vet.

Key Takeaways

• White blood cells (also called leukocytes) are your dog's immune army. They fight bacteria, viruses, parasites, and cancer cells.
• A CBC (Complete Blood Count) test counts the different types of white blood cells and tells your vet what kind of problem your dog's immune system is dealing with.
• Abnormal counts can signal infection, inflammation, cancer, drug reactions, tick-borne disease, or inherited disorders.
• In India, tick-borne diseases (Ehrlichia, Anaplasma) are among the most common causes of dangerous white blood cell abnormalities in dogs.
• Leukemia and lymphoma are cancers of the white blood cells. Lymphoma alone accounts for nearly 80-85% of white blood cell cancers in dogs.
• Most WBC disorders are treatable when caught early. A blood test is the fastest way to find the problem.

What Are White Blood Cells and What Do They Do?

Your dog's blood carries three types of cells: red blood cells (which carry oxygen), platelets (which control bleeding), and white blood cells (WBCs), also called leukocytes.

White blood cells have one job: defend the body against anything that does not belong there. Bacteria, viruses, fungi, parasites, foreign tissue, cancer cells. WBCs find them, attack them, and clean up the debris.

According to the Merck Veterinary Manual, there are two main categories of white blood cells, and they work differently.

Phagocytes: The Eaters

The word phagocyte comes from the Greek word meaning "to eat." These are the cells that engulf and destroy invaders directly.

There are two types:

Granulocytes are named for the granules visible inside them under a microscope. The three types are:

• Neutrophils - the most numerous WBCs. First responders to any bacterial invasion. When you get a "high white blood cell count" reading, neutrophils are usually responsible.
• Eosinophils - involved in fighting parasites and managing allergic reactions.
• Basophils - rare in dogs, but involved in allergic responses.

Mononuclear phagocytes travel from the blood into the body's tissues, where they transform into large cells called macrophages. Think of macrophages as the clean-up crew that arrives after neutrophils have already done the initial fighting.

Lymphocytes: The Strategy Cells

Lymphocytes are the clever ones. Instead of directly attacking pathogens, they remember them and coordinate the immune response.

According to the Merck Veterinary Manual, lymphocytes develop in the bone marrow and then split into three specialised groups:

• T cells - produced in the thymus gland (at the base of the neck). Fight viral infections and cancers. Some T cells are "cytotoxic" (they directly destroy infected cells), while others are "helper" T cells that coordinate the broader immune response.
• B cells - produce antibodies. When a bacterium enters the body, B cells coat it with antibody molecules, marking it for destruction by neutrophils and macrophages.
• Natural killer cells - attack foreign material and cancer cells directly.

If lymphocytes are reduced or abnormal, the dog becomes immunodeficient and highly vulnerable to a wide range of infections.

Lymphocytes also produce immunoglobulins (antibodies). Different classes serve different purposes:

• IgA is found in the lungs and intestines.
• IgM is the first antibody produced against newly encountered threats.
• IgG is the main antibody circulating in the bloodstream.
• IgE is involved in allergic reactions.

All of these cells are produced in the bone marrow, which is the spongy tissue inside bones. This is important to understand because many WBC disorders either start in the bone marrow or affect it.

The Leukogram: Your Vet's Most Useful Tool

A leukogram is the part of a Complete Blood Count (CBC) that counts and examines white blood cells. It tells your vet not just how many WBCs are present, but what types, and whether the cells look normal under a microscope.

According to the Merck Veterinary Manual, leukogram abnormalities generally fall into four categories:

1. Transient physiologic responses (stress, exercise, excitement)
2. Inflammatory, infectious, and immunologic responses (infection, tick disease, immune attack)
3. Bone marrow responses to injury (marrow failure, toxin damage)
4. Cancer of the blood cells (leukemia, lymphoma)

The leukogram defines a process, not always a specific diagnosis. Your vet uses it as a starting point for further investigation.

Two key terms to know:

• Leukocytosis - an increase in the total number of circulating white blood cells
• Leukopenia - a decrease in the total number of circulating white blood cells

Neutrophil Disorders: Too Many or Too Few

Since neutrophils make up the majority of white blood cells, changes in their count are the most common finding on a CBC.

Neutrophilia: Too Many Neutrophils

Neutrophilia is an increase in circulating neutrophils. According to the Merck Veterinary Manual, neutrophilia is caused by inflammation.

When there is a bacterial infection anywhere in your dog's body, the bone marrow releases more neutrophils into the bloodstream to fight it. The more severe the infection, the higher the count.

Your vet may also look at the shape of the neutrophils. During very severe inflammation, the bone marrow pushes out neutrophils before they are fully mature. These immature forms are called band neutrophils. A high number of bands is called a "left shift" and indicates the bone marrow is working extremely hard - a sign of serious systemic infection.

When neutrophils are under severe stress, they can also develop what are called toxic changes - visible structural changes under a microscope that signal overwhelming bacterial infection.

Neutropenia: Too Few Neutrophils

Neutropenia is a decrease in neutrophil count and is more concerning than neutrophilia.

According to the Merck Veterinary Manual, neutropenia can occur because:

• Neutrophils are sticking to the walls of inflamed blood vessels instead of circulating
• The immune system is destroying neutrophils
• The bone marrow has stopped producing them

Neutropenia can occur during overwhelming bacterial infections when the body is consuming neutrophils faster than it can produce them. It also occurs as an adverse reaction to certain drugs.

When combined with low red blood cells and low platelets, a condition called pancytopenia develops. Pancytopenia usually means the bone marrow has stopped functioning, which is a serious finding requiring urgent investigation.

A dog with neutropenia has little defense against bacterial infection. Even a small cut or a routine vaccination can become dangerous.

Eosinophil Disorders: When Parasites and Allergies Show Up in Blood

Eosinophilia: Too Many Eosinophils

Eosinophilia is an increase in eosinophil count. According to the Merck Veterinary Manual, increases are caused by:

• Substances that trigger allergic reactions (like histamine)
• Specific antibodies involved in allergic responses
• Infections with parasites such as heartworms or fleas
• Inflammation of the intestines, kidneys, lungs, or skin

In India, eosinophilia is extremely common in dogs due to the high prevalence of intestinal worm infections (roundworms, hookworms) and heartworm exposure in mosquito-heavy regions.

If your dog has consistently high eosinophil counts alongside digestive symptoms, your vet will likely test for parasites as the first step.

Eosinopenia: Too Few Eosinophils

Eosinopenia (a decrease in eosinophils) is actually quite common and not concerning on its own. It is a normal reaction to stress or to treatment with corticosteroids.

If your dog is on steroids for any condition, expect eosinophil counts to drop. This is expected and does not indicate a new problem.

Lymphocyte Disorders: Your Dog's Antibody Factories

Lymphocytosis: Too Many Lymphocytes

Lymphocytosis is an increase in lymphocyte numbers. According to the Merck Veterinary Manual, it can be caused by:

• Certain hormones (including excitement-related adrenaline release in anxious dogs during blood draws)
• Immune system stimulation from chronic infections
• Chronic inflammatory diseases like arthritis
• Leukemia - cancer of the immune system

When lymphocytosis is extreme, particularly when the cells look abnormal under a microscope, cancer must be ruled out. This requires more specialised testing beyond the standard CBC.

Lymphopenia: Too Few Lymphocytes

Lymphopenia is a decrease in lymphocyte count and is one of the most common WBC abnormalities seen in everyday practice.

The most common cause is corticosteroid treatment - either from medication prescribed by a vet, or from the dog's own body producing high cortisol levels during stress, illness, or conditions like Cushing's disease.

Other causes include:

• Decreased production of lymphocytes (bone marrow failure)
• Certain viral infections - including parvovirus, which is one of the most feared diseases in Indian puppies that are not fully vaccinated (read our guide on Complete Puppy Vaccination Schedule in India)
• Hereditary immunodeficiency diseases

A dog with persistent lymphopenia is immunocompromised. They are more vulnerable to infections that a healthy dog would fight off easily

Monocyte and Basophil Disorders

Monocytosis

Monocytes are WBCs that travel from the bloodstream into tissues, where they become macrophages. Monocytosis (too many monocytes) is associated with long-term, chronic inflammation.

If a dog has had a persistent infection, an abscess, or a chronic disease for weeks or months, monocytes often increase as part of the body's sustained immune response.

Basophilia

Basophils are extremely rare in the blood of healthy dogs. They are involved in allergic reactions and parasite control, similar to eosinophils.

According to the Merck Veterinary Manual, basophilia (an increase in basophils) is uncommon, but does occur in some dogs with heartworm disease. If a dog living in a mosquito-heavy Indian environment shows unexplained basophilia, heartworm testing should be considered.

Leukemia in Dogs: When the White Blood Cells Become the Problem

Leukemia is a malignant cancer where abnormal white blood cells multiply uncontrollably in the bone marrow and flood the bloodstream.

According to the Merck Veterinary Manual, leukemia should be considered a potential cause any time there is an extreme increase in WBC numbers that cannot be explained by infection or inflammation.

The two main types of leukemia in dogs are:

Acute leukemia - rapid onset, aggressive. Abnormal immature blast cells accumulate in the bone marrow and blood. The dog deteriorates quickly. Acute leukemia is very difficult to treat.

Chronic leukemia - slower progression. Mature-appearing but abnormal lymphocytes or granulocytes accumulate over months. Dogs may have no signs initially and are often diagnosed during routine blood tests.

Signs of leukemia can include lethargy, loss of appetite, weight loss, paleness, and a tendency to bleed or bruise easily. The bone marrow is so full of cancer cells that it can no longer produce normal red blood cells or platelets.

Diagnosis requires a CBC, blood smear examination by a specialist, and usually a bone marrow biopsy.

Treatment for acute leukemia in dogs is challenging, and outcomes vary widely depending on the type. Chronic forms may be managed for extended periods. Your vet will likely refer to a veterinary oncologist for a detailed treatment plan.

Lymphoma in Dogs: The Most Common Canine Blood Cancer

Lymphoma is one of the most common cancers in dogs. According to the Merck Veterinary Manual, it is a progressive, potentially fatal disease caused by the uncontrolled growth of lymphocytes. It typically starts in the lymph nodes, spleen, bone marrow, or thymus.

Possible contributing factors include viral infection, environmental exposure to herbicides, genetic abnormalities, and immune system dysfunction.

The Four Forms of Lymphoma

1. Multicentric Lymphoma - by far the most common, accounting for about 80-85% of all cases. The classic early sign is rapid, painless enlargement of the lymph nodes, which may become 3 to 10 times their normal size. In advanced stages, cancerous lymphocytes spread to the spleen, liver, bone marrow, and other organs.

Feel your dog's lymph nodes regularly. The main ones you can feel from outside are under the jaw (submandibular), in front of the shoulder (prescapular), in the armpit (axillary), in the groin (inguinal), and behind the knee (popliteal). If one or more of these feels like a grape, bean, or larger lump that was not there before - see a vet immediately.

2. Alimentary Lymphoma - affects the digestive tract. Signs include vomiting, diarrhoea, abdominal pain, weight loss, and loss of appetite. Less than 10% of canine lymphoma cases are this type.

3. Mediastinal Lymphoma - affects the chest cavity. The thymus or chest lymph nodes enlarge, causing difficulty breathing as fluid accumulates in the chest. Some dogs also drink excessively and urinate more than normal, due to abnormally high calcium levels in the blood - a syndrome seen in 10-40% of dogs with this type.

4. Extranodal Lymphoma - can affect any organ outside the lymph nodes. In the skin, it appears as raised sores or scaly patches. In the kidneys, it causes kidney failure. In the nervous system, it causes seizures. In the eyes, it causes blindness.

Diagnosing Lymphoma

Lymphoma is often relatively straightforward to diagnose. A fine needle aspiration (a thin needle inserted into an enlarged lymph node, no surgery required) usually provides enough cells to confirm the diagnosis. Specialised tests including immunophenotyping can then determine whether the cancer is B-cell or T-cell type, which matters for prognosis.

Treatment and Outlook

According to the Merck Veterinary Manual, treatment of high-grade multicentric lymphoma with combination chemotherapy is often very successful - more than 90% of dogs achieve complete remission (full disappearance of visible tumour).

• Dogs with B-cell lymphoma: expected survival of about 12 months with chemotherapy
• Dogs with T-cell lymphoma: expected survival shorter, around 6 months
• Dogs with low-grade lymphoma: can survive more than two years with treatment

Chemotherapy in dogs is typically much better tolerated than in humans. Hair loss is rare. Most dogs continue to eat well and remain active throughout treatment.

In recent years, treatment protocols have become shorter and more targeted. Bone marrow transplants are now available at some specialist centres, though this remains rare in India.

Without treatment, most dogs with high-grade multicentric lymphoma survive only 4 to 6 weeks after diagnosis.

Gray Collie Syndrome: A Rare but Deadly Inherited Disorder

Gray Collie Syndrome, also called cyclic hematopoiesis, is an inherited immune deficiency that affects gray Collies (not merle Collies - the coat colour distinction matters).

According to the Merck Veterinary Manual, it is caused by a defect in the maturation of the stem cells that produce all blood cells - red blood cells, white blood cells, and platelets - in the bone marrow.

The result is a cyclical pattern: every 12 days, all blood cell counts drop dramatically. Neutrophils are affected most severely.

Signs include:

• Pale coat and nose colour (silver-gray instead of the expected rich grey)
• Recurrent severe bacterial infections during low-neutrophil periods
• Bleeding episodes during low-platelet periods
• Stunted growth in surviving puppies

Most affected puppies die at birth or within their first week. The majority of dogs that survive the neonatal period die by 6 months of age from overwhelming bacterial infections. Even those that survive longer typically die by 3 years of age from amyloidosis - an accumulation of abnormal amyloid proteins in the body's organs.

Treatment with proteins that stimulate neutrophil production in the bone marrow may provide temporary improvement, but there is no long-term cure.

This condition is rare, and if you are planning to breed Collies, DNA testing of breeding stock is strongly recommended to avoid passing on the affected gene.

Pelger-Huet Anomaly: The Harmless Lookalike

Pelger-Huet Anomaly is an inherited condition where neutrophils fail to mature normally - they look immature under the microscope, with fewer nuclear lobes than expected.

The important thing to know about this condition: it is harmless.

According to the Merck Veterinary Manual, white blood cell function is completely normal in dogs with this anomaly. The cells fight infection effectively. The dogs show no signs of illness.

The danger is misdiagnosis. An immature-looking neutrophil can be confused with a "left shift" - the sign of severe infection described earlier. If a vet unfamiliar with this anomaly sees it in a blood smear, they might suspect a severe systemic infection and begin aggressive treatment that is not needed.

If a vet mentions "immature-appearing neutrophils" and your dog has no other signs of illness, Pelger-Huet Anomaly is worth discussing as an alternative explanation. DNA testing can confirm the diagnosis and prevent unnecessary worry and treatment.

Tick-Borne Diseases and White Blood Cell Counts in Indian Dogs

This section matters especially for pet parents in India - and it cannot be skipped.

Ticks are active year-round in India. The warm, humid climate creates ideal conditions for the Brown Dog Tick (Rhipicephalus sanguineus) and the Asian Longhorned Tick, both of which transmit organisms that directly attack the blood cell system.

Ehrlichiosis (Ehrlichia canis)

Ehrlichia canis is transmitted by the Brown Dog Tick and is one of the most common tick-borne diseases in Indian dogs. It attacks white blood cells directly - specifically monocytes and lymphocytes - and also destroys platelets.

On a CBC, a dog with Ehrlichia typically shows:

• Low platelet count (thrombocytopenia)
• Low white blood cell count (leukopenia) in some cases
• Elevated lymphocytes or monocytes in others

Chronically infected dogs can develop severe immune suppression. Some develop a form of bone marrow failure where all blood cell production is compromised. Treatment is doxycycline for a minimum of 28 days.

Anaplasmosis (Anaplasma platys)

Anaplasma platys infects platelets and causes cyclic thrombocytopenia (a pattern of platelet counts rising and falling in 1-2 week cycles). Anaplasma phagocytophilum infects neutrophils directly.

Anaplasmosis in Indian dogs is increasingly recognised and consistently causes WBC count abnormalities alongside its platelet effects.

What This Means for Your Dog's Blood Test

If your dog has any of the following combinations on a CBC - low platelets, low or high WBC, monocytosis, or lymphopenia - alongside signs like lethargy, fever, or poor appetite, ask your vet to run a tick-borne disease panel. This includes serology or PCR testing for Ehrlichia, Anaplasma, and Babesia.

The single most effective thing you can do to prevent these blood disorders is consistent, year-round tick prevention. Our detailed guide on Tick Treatment for Dogs: Best Tick Medicines, Tablets and Complete Protection Guide covers all the options available in India.

NexGard (afoxolaner), available at Animeal with up to 15% off, is one of the most commonly recommended monthly oral tick treatments in India. Consult your vet for the right formulation for your dog's weight.

How Is a WBC Disorder Diagnosed?

Step 1: Complete Blood Count (CBC) with Differential

This is the starting point for virtually every WBC disorder investigation. It counts the total WBC number and breaks it down into each type (neutrophils, lymphocytes, eosinophils, monocytes, basophils). It also checks red blood cells and platelets.

Step 2: Blood Smear Examination

A technician or veterinary pathologist examines a drop of blood under a microscope. This reveals the appearance of the cells - whether neutrophils are mature or immature, whether lymphocytes look abnormal (cancer), and whether parasites are visible inside the cells.

Step 3: Additional Testing Based on Findings

Step 4: Bone Marrow Biopsy or Aspiration

When the bone marrow itself is suspected as the source of the problem (leukemia, aplastic anaemia, bone marrow failure), a small sample is taken from the marrow under anaesthesia or sedation. This procedure is essential for diagnosing leukemia and explaining otherwise unexplained pancytopenia.

Treatment Overview for White Blood Cell Disorders

Treatment depends entirely on the underlying cause. There is no single approach that covers all WBC disorders.

For dogs undergoing chemotherapy or recovering from severe infections, immune support can be valuable during recovery. Himalaya Immunol Liquid, available at Animeal with up to 15% off, is an Ayurvedic immunomodulator containing Guduchi (Tinospora cordifolia) and Ashwagandha (Withania somnifera) that supports the immune system during recovery. Always use it under veterinary guidance, especially if your dog is on concurrent medical treatment.

What Should You Watch For at Home?

You cannot diagnose a WBC disorder at home. But you can catch the warning signs early enough that a vet visit happens before a minor problem becomes a crisis.

Signs that your dog's immune system may be struggling:

Recurring infections that keep coming back after treatment - skin infections, ear infections, urinary infections. A healthy immune system clears these and keeps them away. Recurring infections suggest the WBCs are not working effectively.

Unexplained lethargy that lasts more than 24-48 hours and is not explained by heat, exercise, or a recent vaccination. See our guide on How to Prevent Lethargy in Your Dog for a full breakdown of causes.

Swollen lymph nodes that you can feel under the jaw, in the armpit, or behind the knee. A swollen lymph node is your immune system raising a flag. One swollen node after an infection is expected. Multiple swollen nodes that are painless and growing - go to the vet.

Persistent fever above 39.4 degrees Celsius in a dog. Occasional slight rises are normal. Fever that lasts more than 48 hours or returns repeatedly needs investigation.

Pale gums - press your finger against your dog's gum and release. The white area should turn pink within 2 seconds. If it stays pale, the dog may have severe anaemia, which often accompanies WBC disorders.

Weight loss without dietary change - cancer, chronic infection, and bone marrow disorders all cause progressive weight loss even when a dog is eating.

Prevention in practice:

The most actionable steps for Indian pet parents are consistent vaccination and year-round tick prevention. Parvovirus causes lymphopenia and can devastate a puppy's immune system. Ehrlichia attacks WBCs directly. Both are preventable.

For deworming - intestinal parasites like hookworms cause eosinophilia and anaemia. Regular deworming with a broad-spectrum wormer reduces parasite-driven blood count abnormalities. As discussed in our Bleeding Disorders in Dogs guide, hookworm-related blood loss is a hidden and preventable problem in Indian dogs.

FAQ Section

What does it mean if my dog has a high white blood cell count?
A high WBC count (leukocytosis) usually means your dog's immune system is actively fighting something. Most commonly that is a bacterial infection somewhere in the body. It can also result from stress, steroid use, or, in severe cases, cancer (leukemia or lymphoma). The specific type of WBC that is elevated matters enormously. High neutrophils point to infection. High lymphocytes require further investigation to rule out cancer. Your vet needs the full CBC picture, not just the total count.

Can a dog live normally with lymphoma?
Many dogs with lymphoma, particularly the multicentric B-cell type, live comfortable, active lives during chemotherapy. More than 90% achieve full remission with treatment. The average survival with treatment is around 12 months for B-cell lymphoma. Some dogs, particularly those with low-grade lymphoma, survive well beyond two years. Without treatment, survival is typically 4 to 6 weeks. The quality of life during chemotherapy is generally much better for dogs than for humans - most remain active and continue to eat well.

Are white blood cell disorders common in Indian dogs?
Acquired WBC disorders caused by tick-borne infections (Ehrlichia, Anaplasma) are very common in India, especially in dogs living in apartments in cities like Mumbai, Delhi, Bengaluru, and Pune where tick exposure happens through parks, gardens, and outdoor walks. Lymphoma and leukemia occur at similar rates to global averages. Inherited WBC disorders like Gray Collie Syndrome are rare and specific to certain breeds.

How is lymphoma different from leukemia in dogs?
Both are cancers of the white blood cells, but they originate in different places. Lymphoma starts in the lymph nodes or other lymphoid tissues (spleen, thymus, intestines) and may eventually spread to the blood. Leukemia starts in the bone marrow and floods the bloodstream with abnormal blood cells from the beginning. Lymphoma is far more common. Multicentric lymphoma is often easier to treat than leukemia.

Should I worry if my dog's lymph nodes feel slightly swollen?
It depends. A lymph node that is mildly enlarged during or shortly after an infection (a skin infection, a vaccination reaction, a bite wound) is responding normally. Nodes that shrink once the infection clears are not concerning. Lymph nodes that are painlessly enlarged, feel firm or rubbery, keep growing, or appear at multiple sites simultaneously are warning signs that require veterinary attention within 24 to 48 hours. Do not wait weeks to see if they resolve.

Does a CBC always catch a WBC disorder?
A CBC is an excellent screening tool but it is not the complete picture. Some forms of lymphoma can be present for weeks or months before the CBC becomes abnormal. Similarly, early-stage bone marrow disorders may only show subtle changes. If your dog has clinical signs (swollen nodes, weight loss, recurring infections) but a normal CBC, ask your vet about follow-up testing. A blood smear review by a veterinary pathologist or a lymph node aspiration may detect what the automated count missed.

References

1. R. Darren Wood, DVM, DVSc, DACVP, Ontario Veterinary College, University of Guelph. White Blood Cell Disorders of Dogs - Pet Owner Version. Merck Veterinary Manual. Reviewed/Revised December 2017, Modified June 2026. https://www.merckvetmanual.com/dog-owners/blood-disorders-of-dogs/white-blood-cell-disorders-of-dogs
2. Susan M. Cotter, DVM, DACVIM, Cummings School of Veterinary Medicine, Tufts University. White Blood Cells of Dogs - Pet Owner Version. Merck Veterinary Manual. Reviewed/Revised December 2017, Modified September 2024. https://www.merckvetmanual.com/dog-owners/blood-disorders-of-dogs/white-blood-cells-of-dogs
3. R. Darren Wood, DVM, DVSc, DACVP. Overview of Leukocyte Disorders in Animals - Professional Version. Merck Veterinary Manual. Reviewed/Revised January 2022, Modified March 2026. https://www.merckvetmanual.com/circulatory-system/leukocyte-disorders/overview-of-leukocyte-disorders-in-animals
4. Timothy M. Fan, DVM, PhD, DACVIM, University of Illinois. Malignant Lymphoma in Dogs - Pet Owner Version. Merck Veterinary Manual. Reviewed/Revised December 2017, Modified September 2024. https://www.merckvetmanual.com/dog-owners/blood-disorders-of-dogs/malignant-lymphoma-in-dogs
5. Susan M. Cotter, DVM, DACVIM. Introduction to Blood Disorders of Dogs. Merck Veterinary Manual. Reviewed/Revised December 2017, Modified May 2026. https://www.merckvetmanual.com/dog-owners/blood-disorders-of-dogs/introduction-to-blood-disorders-of-dogs