What Are White Blood Cells?
White blood cells (WBCs), also called leukocytes, fight infection. They move throughout your body in your blood, looking for invaders. Your body is continuously making a fresh supply of WBCs.
About 1% of your blood is made up of WBCs, which are divided into five types:
- Neutrophils. The most common type of WBCs, these cells protect your body from infection by killing and digesting bacteria and fungi.
- Monocytes. They also help protect against infection by breaking down bacteria and fungi.
- Lymphocytes. These create antibodies to fight against bacteria, viruses, and other potential invaders. T cells, natural killer cells, and B cells are all lymphocytes.
- Basophils. These small cells secrete chemicals, such as histamines, that are released during allergic reactions. They might make you cough or sneeze, but that's another way of fighting disease.
- Eosinophils. They identify and kill parasites and cancer cells and help basophils with allergic responses.
Neutrophils
Neutrophils account for 55%-70% of all your WBCs. They're the front line of defense when your body's immune system is attacked. They find and destroy bacteria and fungi by consuming them. Your body reacts by inflammation (redness and swelling), but this is all part of the healing process.
Neutrophils are formed in your bone marrow and carried through your body's blood, tissues, and lymph nodes. These cells are clear and normally round, though they do change shape when fighting disease.
If you have too few neutrophils (a condition called neutropenia or leukopenia), your risk of infection increases a lot. You might develop painful sores in your mouth or anus (bottom), or get unusual illnesses. Neutropenia is often a side effect of cancer-fighting drugs or radiation therapy. These kill cells, both the healthy and unhealthy ones. Neutropenia could also be the result of an autoimmune disease, such as lupus or rheumatoid arthritis, or a bone marrow disease like leukemia.
The normal range for neutrophils in a healthy person is between 2,500 and 6,000 neutrophils per microliter of blood. If your levels are below 1,500, you have neutropenia. There are three classifications:
- Mild: 1,000 to 1,500 neutrophils per microliter of blood
- Moderate: 500 to 1,000 neutrophils per microliter of blood
- Severe: below 500 neutrophils per microliter of blood
Keep in mind that most of the time, a low WBC count is nothing to worry about. If you have mild neutropenia, you probably don't need any treatment or have any symptoms. You only need to be concerned if you have moderate or severe neutropenia.
White Blood Cell Test
Your doctor may order a WBC test if you come to see them with certain health problems. A technician will draw your blood and send it to a lab for a complete blood count, or CBC.
Your WBC count is one of the numbers you get back from this test, along with your red blood cell count and your platelet count. It may point toward or confirm a diagnosis, or show whether a treatment is working or not. It will also tell whether your WBC is higher or lower than it should be.
Normal White Blood Cell Count
Each lab will have its own set of normal values for each blood cell count, called the reference range. The normal reference range is usually 4,000-11,000 WBCs per microliter of blood but can vary depending on the lab.
Normal ranges can also vary depending on the age, race, and sex of the person getting the blood test. Here are the normal WBC ranges for:
- Men and people with male anatomy: 5,000-10,000 WBCs
- Women and people with female anatomy: 4,500-11,000 WBCs
- Children: 5,000-10,000 WBCs
Low White Blood Cell Count
A blood test that shows a WBC count of less than 4,000 per microliter (some labs say less than 4,500) could mean your body may not be able to fight infection the way it should. A low number is called leukopenia or neutropenia. Leukopenia can either be acute or chronic.
Acute leukopenia: It is a short-term condition that is usually due to a temporary illness.
Chronic leukopenia: Leukopenia is considered chronic if you've had a low neutrophil level on at least three occasions over a period of 3 months. It is usually caused by:
- An ongoing illness (such as cancer)
- A viral illness such as HIV
- A genetic condition
- An autoimmune disorder such as lupus
Many people of African and Middle Eastern descent have lower WBCs than other ethnic groups. For instance, African American women may have WBC counts that are on average 25%–40% lower than those of American women of European ancestry. The difference has been linked to a genetic variant more common in people of African descent, which provides protection against malaria and also regulates the production of neutrophils.
Your white blood cell count can rise and fall during the day. One study showed that WBCs seemed to rise and fall in an hourly rhythm. But if you have leukopenia, your WBC remains low and does not rise.
Low White Blood Cell Count Causes
Your doctor will do a physical exam and consider your symptoms along with your past medical issues to figure out what's behind your test result. A very low WBC count could be due to any of the reasons below:
Infection: This is the most common cause of neutropenia in adults. Viruses can affect your bone marrow and cause low WBCs for a while. Severe infections, such as blood infections, can cause your body to use up WBCs faster than it can make them.
Medicines: This is the next most common cause. Chemotherapy drugs, in particular, will destroy healthy WBCs while killing off cancer cells. Radiation therapy can have the same effect. Other drugs that can lower WBCs include antihistamines, antihypertensives, antipsychotics, immunosuppressants, anti-epilepsy drugs, and steroids. Not everyone who takes these drugs has their WBC count drop. It could be that genes play a role in whose WBC count decreases.
Bone marrow problems: The spongy center of your bones, which is called the bone marrow, makes blood cells. Low WBC counts are often linked to bone marrow problems. Being around certain chemicals, such as benzene and pesticides, as well as some types of cancer and cancer treatments including chemotherapy and radiation, can hurt your bone marrow's ability to make WBCs.
Autoimmune disorders: Some autoimmune diseases, such as lupus and rheumatoid arthritis, will tell your body to attack and destroy its own WBCs.
Nutrition: Not eating well or low levels of certain vitamins, such as folic acid and B12, can affect how your body makes WBCs. Alcohol abuse can mess with the nutrients in your body as well as your WBC counts.
Spleen problems: The spleen also makes WBCs. Infections, blood clots, and other problems can make it swell and not work the way it should. This will drop your WBC count.
HIV. This virus (which causes AIDS) weakens your immune system by destroying your T cells, making you unable to fight off even minor infections.
Benign ethnic neutropenia: Some people have naturally low neutrophil counts of under 1,500 per microliter. It's most often seen in people of African descent, though many people of Middle Eastern descent and a few people of European background may have it as well. This condition is called benign ethnic neutropenia because the people who have it are not at a higher risk of infection. It's estimated that 25%-50% of African Americans have a neutrophil count of under 1,500 per microliter, while less than 1% of white Americans do.
Low White Blood Cell Count Symptoms
You may not have any symptoms from having a low WBC count, but it leaves you prone to infections. As a result, you could have:
- Fever
- Rashes
- Mouth ulcers that don't heal
- Sores around the anus
- Pneumonia and other severe illnesses
- Tiredness
You may have these symptoms suddenly, a few days after getting a low WBC count, or after a longer period. Symptoms could come and go if your WBC count is rising and falling, due to say, a medication dose.
Follow-up Tests
If there's no clear reason for a low WBC count, your doctor will probably want to do the test again or do a differential or “diff” along with the CBC.
This other test gives a lot more detail. There are normal ranges for each of the five kinds of WBCs, and some problems only affect one type. The results of a diff could help your doctor narrow down what's going on.
Many times, a repeated test will show that your WBC count is normal.
Your doctor could order more tests, based on the symptoms you have. For instance, you might get checked for strep throat or mono. Other blood tests can look for a viral infection, inflammation, or allergies. The doctor may want to take a sample of your bone marrow to see if it's healthy.
Your doctor may also order a urine test to check for a urinary tract infection, or a chest X-ray if they suspect pneumonia.
What Happens Next?
Sometimes, leukopenia goes away on its own. Other times, if you stop taking the drug that's causing it, or treat the underlying condition, your WBC will increase.
Treatment involves:
- Taking antibiotics or antivirals to get rid of the infection
- Taking drugs to stimulate the production of neutrophils in your bone marrow (usually given as an injection)
- Undergoing a bone marrow transplant in serious cases, such as aplastic anemia or leukemia
Your doctor may ask you to see a hematologist. This is a specialist who has extra training for diagnosing and treating blood count problems.
If your WBC count stays low or keeps getting lower, work with your doctor to find out why it's happening. The right treatment should help your WBC count return to normal.
Prevention
There's no way to prevent leukopenia, but there are ways to keep healthy and lessen infection risk.
- Wash your hands frequently with soap and water or a hand sanitizer.
- Stay up to date on your vaccines, including your flu and COVID shots.
- Avoid crowds, or wear a mask in a crowd.
- Prevent the spread of germs in the kitchen by washing fruits and vegetables before eating, using a separate cutting board for meat to avoid cross-contamination, and cooking meat to the proper temperature.
- Wear gloves when picking up pet waste or infant diapers with poop. Wash your hands when you've finished the task.
How to Increase White Blood Cells
Current research doesn't show that there's any specific diet that will increase your body's production of WBCs. But our bodies do use materials in proteins to make WBCs. Therefore you should:
- Eat high-quality proteins including fish, poultry, beef, eggs, milk, Greek yogurt, and beans.
- Take vitamin B12 and folate (folic acid), or a multivitamin with those ingredients, if you don't eat these proteins. The body uses vitamin B12 and folate to make WBCs.
If you're having chemotherapy, talk to your doctor or nutritionist before taking supplements because some of them shouldn't be taken with some cancer treatments.
Takeaways
If you have a low WBC count, most of the time it's nothing to worry about. However, if your count is below 4,000 per microliter, you have neutropenia, aka leukopenia, and you'll need treatment. Treatment depends on the reason for the low WBC but generally involves giving antibiotics to fight any infections you might have. In some cases, you may need a bone marrow transplant or drugs to stimulate the production of neutrophils in your bone marrow.
Low White Blood Cell Count FAQS
What is a dangerously low white blood cell count?
Anything below 4,000 WBCs per microliter. And if your neutrophil count is below 500 cells per microliter, your risk of getting infections will increase greatly. You might even get infections from bacteria that normally live in your mouth with no complications.
How can I raise my white blood cell count?
It depends on the reason for the low WBC. If it's due to an illness or disease, treating the illness will raise your WBC. If you're on chemotherapy, stopping that or changing your medication should raise your WBC. Foods rich in protein, vitamin B12, and folate are all building blocks used by your body to make WBC, so taking them can be helpful.
