Why Does My White Blood Cell Count Decrease? 8 Potential Causes and What to Do

Envision your immune system as a security team—when your white blood cell count drops, it’s like losing guards on duty, leaving you more vulnerable. You may notice frequent infections, fatigue, or slow healing, and contemplate what’s causing the dip. From viral infections messing with bone marrow to nutrient deficiencies or medication side effects, several factors could be at play.

Viral Infections That Temporarily Disrupt Bone Marrow Function

At the time certain viruses invade your body, they can temporarily throw off your bone marrow’s ability to produce white blood cells—your frontline defenders against illness.

At the moment you catch a viral infection like Epstein-Barr or hepatitis, your immune response shifts focus, sometimes slowing WBC production. This leads to leukopenia, a drop in your white blood cell count, which shows up on complete blood counts.

Viruses like flu or CMV can also directly affect bone marrow, causing temporary disruptions in cell creation.

The positive aspect? This dip usually reverses once the infection clears, often within weeks.

Should your CBC shows low WBCs during illness, don’t panic—it’s likely your body prioritizing fighting the virus over making new cells.

Just monitor symptoms and let recovery run its course.

Autoimmune Disorders Attacking White Blood Cells

Several autoimmune disorders can turn your body’s defenses against itself, mistakenly destroying white blood cells (WBCs) like a case of friendly fire.

Conditions like lupus or rheumatoid arthritis often trigger your immune system to attack WBCs, lowering your WBC counts—a condition called leukopenia. This leaves you more vulnerable to infections since your body struggles to fight off invaders.

Chronic inflammation from these disorders can also damage WBC production, making the problem worse.

Even treatments like immunosuppressive therapies, meant to calm an overactive immune system, may further drop your WBC levels.

Should you notice frequent sickness or fatigue, talk to your doctor—they can check your WBC counts and adjust treatments to balance protection without compromising your defenses.

Severe Bacterial Infections Depleting White Blood Cells

Severe bacterial infections can drain your white blood cells as they fight hard against the invaders, sometimes faster than your body can replace them.

Conditions like sepsis trigger a rapid drop in WBCs, leaving you more vulnerable to further infections.

Certain bacterial toxins even directly attack these cells, worsening the depletion.

Bacterial Toxins Destroying WBCS

Whenever bacterial infections turn severe, they don’t just attack your body—they target the very cells defending you. Certain bacteria release toxins that directly destroy your white blood cells, lowering your count and weakening your immune response.

This condition, called leukopenia, leaves you vulnerable to worsening infection. Some bacteria, like those causing pneumonia or meningitis, overwhelm your system, triggering inflammation that further depletes white blood cells. Your body might also redirect these cells to the infection site, reducing their presence in your bloodstream.

Should you notice persistent fever, fatigue, or rapid heartbeat, it could signal a severe bacterial infection affecting your white blood cell count.

Prompt treatment with antibiotics can help stop the damage and stabilize your levels, so don’t ignore these warning signs.

Sepsis-Induced Leukocyte Depletion

At the time your body fights a severe bacterial infection, it can sometimes overreact, leading to sepsis—a life-threatening condition that drains your white blood cells.

When sepsis strikes, your immune system goes into overdrive, releasing chemicals that eventually overwhelm your bone marrow’s ability to produce enough white blood cells.

A blood test could reveal leukopenia, or low white blood cell counts, which weakens your defenses and raises the risk of secondary infections.

The infection itself, combined with your body’s extreme response, depletes these essential cells, leaving you vulnerable.

Should you be diagnosed with sepsis, quick treatment is key to stabilizing your immune system and preventing further damage.

Without intervention, this cycle can worsen, so don’t ignore sudden fatigue or fever—seek help immediately.

Nutritional Deficiencies in Vitamin B12 and Folate

Should your body not be receiving enough vitamin B12 or folate, it can disrupt your white blood cell count, leaving you more vulnerable to infections. Nutritional deficiencies in these vitamins often lead to leukopenia—a drop in white blood cells—since they’re essential for healthy cell production.

Without enough B12, your body struggles to make DNA for new blood cells, while low folate messes with cell division. You may not get enough from dietary intake, especially in case you eat few animal products (for B12) or skip leafy greens (for folate).

In the event that you have malabsorption conditions like celiac disease or gut surgery, absorbing these nutrients gets even harder. To fix this, eat more B12-rich foods like eggs or fortified cereals and load up on folate-packed lentils or spinach.

A blood test can confirm whether you’re low, so talk to your doctor.

Medications That Suppress White Blood Cell Production

Because some medications interfere with your bone marrow’s ability to produce white blood cells, your immune system can take a hit. Chemotherapy drugs are a common culprit—they target fast-growing cells, including those in your bone marrow, which can lead to leukopenia (low white blood cell counts).

Antibiotics, especially certain broad-spectrum ones, may also suppress production, leaving you more vulnerable to infections. Should you be treating autoimmune diseases, medications like corticosteroids or biologics can dial down your immune response, sometimes too much.

Even some pain relievers or anti-seizure drugs may play a role. Your doctor will likely monitor your blood counts closely in case you’re on these meds. Should your levels drop, they may adjust your dosage or suggest alternatives to keep your immune system strong.

Chemotherapy and Radiation Therapy Side Effects

While you’re going through chemotherapy or radiation, your white blood cell count can drop because these treatments don’t just target cancer—they also affect healthy cells that grow quickly, like those in your bone marrow. This can lead to leukopenia (low white blood cells) or neutropenia (low neutrophils), making you more prone to infections. Your doctor will monitor your blood counts closely and might adjust dosages to reduce risks.

Stay proactive—hydration, rest, and avoiding crowds can help. Your team’s got you.

Bone Marrow Diseases Affecting Cell Production

Chemotherapy and radiation aren’t the only things that can lower your white blood cell count—bone marrow diseases play a big role too. Your bone marrow is where your body works to produce blood cells, and whenever it’s damaged or diseased, your white blood cell count can drop lower than normal.

Conditions like aplastic anemia mean your marrow can’t make enough healthy cells, leaving you vulnerable to infections. Leukemia, on the other hand, floods your marrow with abnormal cells, crowding out the ones you need. Neutropenia—a shortage of infection-fighting neutrophils—often follows.

Should you be managing these issues, your doctor will monitor your counts closely. Treatments like medications or transplants could assist, but the initial step is comprehending what’s happening in your marrow.

Steps to Take When Your White Blood Cell Count Is Low

Monitor for infections by checking for signs like fever or unusual fatigue, and report them to your doctor right away.

Maintain hygiene practices—wash your hands often, avoid sick people, and keep cuts clean to lower infection risks.

Ask your doctor whether adjusting treatments, like medications or supplements, could help boost your white blood cell count.

Monitor for Infections

At the time your white blood cell count drops, your body struggles to fight off germs, making you more likely to get sick. A low white blood cell count increases your risk of infection, so it’s essential to monitor for infections closely.

Watch for signs like fever, chills, or unusual fatigue—these could mean trouble. Regular complete blood count tests help track your levels, particularly in case you’re undergoing cancer treatment.

Practice good hygiene to lower your exposure to germs, but don’t stop there. Report symptoms to your doctor immediately, even though they seem minor.

Prompt action can prevent complications. Stay alert, keep in touch with your healthcare team, and trust your instincts—your body’s signals matter.

Maintain Hygiene Practices

Keeping infections at bay starts with smart hygiene habits while your white blood cell count is low. Since a low WBC weakens your defenses, maintaining hygiene practices becomes your best shield against illness.

Wash your hands often with soap—especially before eating or touching your face—to slash the risk of infection. Skip crowded spots and steer clear of sick friends to dodge germs.

Should you’ve had cancer treatments or other conditions that drop WBCs below the normal range, extra caution matters. Cook meat thoroughly, avoid raw foods, and sanitize surfaces to block bacteria.

Keep cuts clean and covered, and stay up-to-date on vaccines like flu shots. Small steps add up to big protection while your body’s fighting power is down.

Adjust Medical Treatments

At the time your white blood cell count drops, adjusting your medical treatments could be the key to staying safe and giving your body a chance to recover. Should you be undergoing chemotherapy, your doctor could pause or delay it to let your immune system rebuild. They might also prescribe growth factors like Filgrastim to boost WBC production, particularly in the event that your neutrophil count falls too low. Antibiotics or antivirals could be needed to fight infections while your counts are down. Regular blood tests help track progress, so don’t skip them.