Yes, COVID-19 can cause neutropenia, a condition where your body has abnormally low levels of neutrophils, the white blood cells that serve as your front line of defense against bacterial infections. It has been documented across all severity levels of COVID-19, from completely asymptomatic infections to severe cases requiring hospitalization. The drop in neutrophils can happen during the acute illness or show up weeks after you’ve seemingly recovered.
How Common Is It?
The prevalence varies quite a bit depending on the group studied, but the numbers are significant enough to take seriously. A case series of 43 pediatric patients in Rome found neutropenia in 26% of them. A larger retrospective study of 95 children in Milan reported mild neutropenia in about 12.6%. A smaller series from China found decreased neutrophil counts in 30% of pediatric patients. These studies lean heavily on children, partly because neutropenia after viral infections tends to be more commonly recognized and studied in younger patients, but the condition is not limited to kids.
Notably, severity of the COVID infection itself doesn’t predict whether you’ll develop neutropenia. Mild and even asymptomatic infections have triggered it. Two infants with only mild COVID-19 symptoms developed severe neutropenia, with neutrophil counts dropping to just 244 and 482 cells per microliter, well below the normal range of 1,500 to 8,000.
Why COVID Lowers Neutrophil Counts
There are several overlapping reasons this happens, and researchers believe more than one mechanism can be at work in the same patient.
The most straightforward explanation is bone marrow suppression. Your bone marrow is where neutrophils are made, and viral infections can disrupt that factory. SARS-CoV-2 may damage the stem cells that produce blood cells either by infecting them directly or by triggering an intense immune response that harms them as collateral damage. When your immune system fights the virus, it releases inflammatory signaling molecules that can push those stem cells toward self-destruction. Immune cells meant to target the virus sometimes turn on the blood-forming cells instead, causing them to die off faster than they’re replaced.
A second mechanism involves neutrophils getting trapped in the lungs. Research using live imaging in mice found that SARS-CoV-2 infection causes neutrophils to stick to the walls of blood vessels in the lungs for much longer than normal. These neutrophils essentially pile up in the pulmonary circulation rather than flowing freely through the bloodstream. When a blood sample is drawn from your arm, those sequestered neutrophils don’t show up in the count, making it look like you have fewer than you actually do. This trapping also contributes to the blood clotting problems and impaired blood flow seen in COVID lung disease.
A third possibility is autoimmune disruption. The intense immune activation from COVID can sometimes cause the body to produce antibodies that mistakenly target its own neutrophils, destroying them faster than the bone marrow can replace them. This mirrors a well-known pattern seen with other viral infections.
When It Appears and How Long It Lasts
The timing is unpredictable. Some patients show low neutrophil counts during the active infection. Others develop neutropenia weeks after they’ve recovered and their other lab work has returned to normal.
One well-documented case involved a 22-year-old man who was hospitalized for COVID pneumonia, discharged with completely normal blood counts, and then developed neutropenia about two weeks later. His neutrophil count continued dropping during a second hospitalization, bottoming out at just 190 cells per microliter, which is critically low. Yet within about a week of that nadir, his counts rebounded to a normal 2,810 without any specific treatment for the neutropenia itself.
That pattern of spontaneous recovery is common but not universal. Most cases of COVID-related neutropenia resolve on their own within a few weeks. However, at least one case report describes a patient whose bone marrow suppression lasted four months before finally normalizing. The prolonged cases are less well understood, partly because they’re rare enough that large-scale data doesn’t yet exist. The key variable seems to be whether the bone marrow has been temporarily stressed or has sustained more lasting immune-mediated damage.
COVID Treatments That Can Also Cause It
If you’re being treated for COVID with certain medications, the drugs themselves can independently lower your neutrophil count, making it harder to tell whether the virus or the treatment is responsible.
Tocilizumab, an immune-modulating drug used in severe COVID, causes neutropenia in about 1.5% of patients. Sarilumab, a similar drug, has been associated with significantly low neutrophil counts in roughly 6% of patients treated for inflammatory conditions. JAK inhibitors like baricitinib, also used in COVID treatment, have shown a better safety profile in this regard, with studies finding no significant increase in adverse events compared to control groups.
The practical takeaway: if you develop neutropenia while being treated for COVID, the cause could be the virus, the medication, or both. Distinguishing between them matters because the management approach differs.
What Neutropenia Feels Like
Neutropenia itself doesn’t cause symptoms you’d notice. You won’t feel your neutrophil count dropping. What you might notice are the consequences: unusual susceptibility to infections, fevers that seem disproportionate to what’s causing them, or infections that don’t respond to treatment the way they normally would. Mouth sores and skin infections can also be signs. Most people find out about their neutropenia through routine blood work rather than from any specific symptom.
The risk depends on how low your count drops. Mild neutropenia (counts between 1,000 and 1,500 cells per microliter) often causes no noticeable problems. Severe neutropenia (below 500) puts you at meaningful risk for serious bacterial and fungal infections because your body has lost much of its first-response defense system.
How It’s Managed
For most people with COVID-related neutropenia, the approach is watchful waiting with regular blood count monitoring. Since the majority of cases resolve spontaneously, aggressive treatment isn’t always necessary.
When counts drop dangerously low or don’t recover on their own, a growth factor medication called G-CSF can stimulate the bone marrow to produce more neutrophils. European Hematology Association guidelines recommend using it to keep neutrophil counts above 1,000 per microliter in both children and adults. However, there’s an important caveat specific to COVID: overdosing G-CSF can worsen the inflammatory response in the lungs, potentially causing more tissue damage. The goal is to nudge counts up to a safe range without fueling the kind of excessive inflammation that makes COVID dangerous in the first place.
For patients whose neutropenia appears to be driven by an autoimmune mechanism, where the immune system is actively destroying neutrophils, immunosuppressive medications can help calm that response. In one study, patients with COVID-associated bone marrow failure responded to cyclosporine, supporting the theory that the immune system’s overreaction to the virus was driving the problem rather than the virus itself doing direct damage.