A low number of lymphocytes can happen if you take certain medications, have an infection or a health condition, including an autoimmune disease, or have an inherited condition.

Lymphocytopenia, also referred to as lymphopenia, occurs when the lymphocyte count in your blood is lower than usual. Severe or chronic low counts can indicate a possible infection or other illness and should be investigated by your doctor.

Lymphocytes are a kind of white blood cell. They’re part of your immune system. These essential cells circulate in blood and lymph fluid. They defend your body by attacking at the first sign of an invasion by harmful organisms. Lymphocytes also play a key role in triggering other immune actions and help build your body’s immunity through past infections and vaccinations.

There are three main types of lymphocytes that work together to help identify and eliminate infections and other diseases:

  • B cells make antibodies and signaling proteins that help flag or attack invading bacteria, viruses, and toxins.
  • T cells communicate with B cells and seek and destroy the cells that have become infected or are cancerous.
  • Natural killer (NK) cells contain compounds that can kill cancer tumor cells and cells infected with a virus.

Low levels of T cells or too few NK cells can lead to uncontrolled viral, fungal, and parasitic infections. B-cell lymphocytopenia can lead to an increase in harmful and different types of infections.

Lymphocytopenia may be a sign of an underlying illness, condition, or another factor. Causes are usually acquired, which means that you develop rather than inherit them.

T cells make up the greatest proportion of lymphocytes, and T-cell lymphocytopenia is the most common. However, this condition can affect all three cell types.

Autoimmune disorders

Autoimmune disorders occur if the immune system is in overdrive and incorrectly attacks the body’s cells and tissues. These can include:

Certain immunosuppressant medications used to treat autoimmune disorders may cause lymphocytopenia.

Cancer and treatments for cancer

Cancer — especially blood or lymphatic cancers like lymphoma (such as Hodgkin’s lymphoma), Kaposi sarcoma, and leukemia — can result in low lymphocyte levels.

The following cancer treatments may also result in lymphocytopenia:

Diseases that affect the blood and bone marrow

These conditions can cause low lymphocyte levels:

Infections

Viral, bacterial, parasitic, and fungal infections are common causes of lymphocytopenia. Any type of infection may cause your lymphocyte count to fall. For example:

Lymphocytopenia may be a sign of sepsis or acute bacteremia. Sepsis is a severe infection that causes systemic inflammation and acute bacteremia is a bacterial presence in the blood that could lead to sepsis. Both instances require urgent medical attention.

Inherited causes

Inherited or congenital causes of lymphocytopenia are rare. Some of these are:

  • ataxia-telangiectasia
  • DiGeorge syndrome
  • severe combined immunodeficiency
  • Wiskott-Aldrich syndrome

Nutritional causes

Malnutrition or undernutrition is a common global cause of lymphocytopenia. This occurs when the body lacks protein and other nutrients necessary to produce lymphocytes.

An eating disorder, such as anorexia nervosa, may lead to reduced-production lymphocytopenia.

Gastrointestinal conditions

Conditions that damage the gut wall can affect the body’s absorption of nutrients and may lead to lymphocytopenia in some cases. These are generally referred to as protein-losing enteropathy and include:

According to research from 2008, a deficiency of the mineral zinc in your diet can weaken immune health by causing T-cell lymphocytopenia and other immune system dysfunction.

Medications

In addition to cancer treatments, several drugs can reduce lymphocytes. Medication-induced lymphocytopenia ranges from minor to severe.

The following medications may lower your lymphocyte level:

Kidney disease

Kidney disease, particularly late stage chronic disease, can reduce the number of T cells in the blood, but lymphocytopenia can also occur in acute kidney injury.

Trauma and surgery

Trauma from an injury or acute emergency such as cardiac failure can lower lymphocyte counts. Undergoing surgeries such as cardiac bypass can also cause lymphocytopenia.

Other causes

Other causes of lymphocytopenia include stress and alcohol misuse.

Additionally, there is a rare condition known as idiopathic CD4-positive lymphocytopenia, in which the cause is unknown.

You may be at risk of lymphocytopenia if:

  • you’ve had a recent infection or surgery
  • you have an underlying condition that can cause lymphocytopenia
  • you’re taking any medications that may affect your lymphocyte count

Older adults and those who are malnourished are particularly at risk.

You may not notice any symptoms of lymphocytopenia. In some cases, you may experience symptoms of the underlying cause or condition. For example:

A complete blood count (CBC) with differential can determine your lymphocyte level. Your doctor may also recommend a special blood test called a lymphocyte profile, also known as a lymphocyte subset panel, to determine the counts of T, B, and NK cells in the body.

A diagnosis of lymphocytopenia means that your blood lymphocyte count is below 1,500 cells/microliter. Infants and children have more lymphocytes, so fewer than 2,000 cells/microliter is considered too low for children under age 6.

Treatment depends on the cause and treating the underlying factor usually resolves lymphocytopenia. You may also require therapy to prevent infections or other complications due to a compromised immune system.

If a medication is causing low counts, your doctor may stop or change the medication. Drug-related lymphocytopenia usually clears up after a person stops taking the drug.

For other causes, your doctor may prescribe the following medications:

  • antiretroviral combination therapy for HIV
  • other antiviral agents, antibiotics, antifungals, or antiparasitic drugs to treat specific infections
  • gamma globulin to help prevent infections that can occur due to B-cell lymphocytopenia
  • bone marrow stem cell transplant

Lymphocytopenia is a common diagnosis from a complete blood count test. Some people may have values slightly less than the usual range without any reason. Low counts are also common in older adults with no concerning symptoms.

This condition may reflect illness, recent surgery, or drug therapy and is usually reversible. Your doctor will look over your current and previous medical history to see if the lymphocytopenia is a new condition. Most cases resolve spontaneously without medical care.

If you receive a diagnosis of acute lymphocytopenia, your doctor will carefully monitor your levels with follow-up blood tests. You may need further tests and treatment to address the main cause. This may involve specialist referrals, blood tests, imaging, or a bone marrow biopsy.

Follow all recommendations and speak with your doctor or nurse if anything is unclear. Lymphocytopenia may indicate or lead to serious illness that can be fatal. Treatment and careful attention to your health are necessary to rebuild your weakened immune system and stay healthy.

You may not be able to fully prevent lymphocytopenia, but you can help boost your immune system and protect yourself against infections. Follow a healthy diet plan, get plenty of rest, and avoid germs as your body recovers its lymphocyte levels.

Eat a nutrient-rich diet to feel better and more energized. Your doctor or nutritionist can help you choose whole foods that are right for you and are packed with protein and healing minerals and vitamins.

Your doctor may also prescribe a special diet if you have a weakened immune system. This includes choosing and preparing foods to avoid germs and related illnesses.

Wash your hands thoroughly with warm, soapy water several times a day to help prevent illness. Use a hand sanitizer if you’re out and avoid crowded areas.

Stay away from animals or ask someone else to clean up after pets. Additionally, be very careful or avoid activities that may cause cuts, scrapes, or even nicks on your skin.

Ask friends and family members to delay visiting you if they’re not feeling well.