Immune defense is how your body’s immune system protects you from infections, harmful or foreign substances, and other threats. It relies on white blood cells, chemical signals, and tissues that work together to identify and neutralize harmful invaders.
Your immune system is essential for fighting off infections and helping you recover from illnesses. When it isn’t functioning properly, you may be more likely to experience frequent or severe infections, slower healing, and chronic inflammation. Monitoring immune markers can reveal when white blood cell levels are too high or too low, or when specific subtypes are out of balance. These changes may signal that further testing is needed.
For people who live with chronic conditions, autoimmune diseases, infections, or treatments that weaken the immune system, monitoring is critical. Guidelines from public health authorities highlight that people who are immunocompromised often need tailored prevention strategies, such as adjusted vaccination schedules. Tracking immune-related blood markers can provide a window into how well this system is functioning. While these tests don’t diagnose a specific condition by themselves, they can help you and your healthcare provider recognize patterns, monitor ongoing health, and guide next steps.
Lab testing through Hers is built around key biomarkers that reflect how your body is performing across major health systems. Each test focuses on high-impact indicators chosen to give you the clearest picture of your well-being and where to take action next. Instead of testing everything, Hers zeroes in on the markers that matter most for guiding long-term health improvements.
Immune defense testing focuses on blood markers that reflect the number and balance of white blood cells. These provide helpful context, but they should always be interpreted alongside your medical history and symptoms.
Basophils (absolute count) Advanced plan
Basophils are a type of white blood cell that help your body respond to allergens and fight certain parasites.
Basophils (percentage) Advanced plan
Basophils typically make up less than 1% of your total white blood cells and help trigger allergic responses and fight certain parasites. A healthy percentage means your blood contains the expected proportion of basophils, which are important for normal immune function.
Eosinophils (absolute count) Advanced plan
Eosinophils are a type of white blood cell that help to control allergy-related inflammation and protect against certain parasites. A healthy count means your blood contains the expected number of eosinophils, which are important for normal immune function.
Eosinophils (percentage) Advanced plan
Eosinophils normally make up about 1-4% of your total white blood cells and help your body fight parasites and control allergy-related inflammation. A healthy percentage means your blood contains the expected proportion of eosinophils, which are important for normal immune function.
Lymphocytes (absolute count) Advanced plan
Lymphocytes are a type of white blood cell that play a key role in building long-term immunity by recognizing and attacking viruses. A healthy count means your immune system is equipped to defend against infections and maintain balance.
Lymphocytes (percentage) Advanced plan
Lymphocytes typically make up 20-40% of your total white blood cells and help your body fight viral infections while building long-term immunity. A healthy percentage means your blood contains the expected proportion of lymphocytes, which are important for normal immune function.
Monocytes (absolute count) Advanced plan
Monocytes are a type of white blood cell that help your body defend against bacteria and clean up damaged cells. A healthy count means your immune system is working efficiently to support your healing and protect against infection.
Monocytes (percentage) Advanced plan
Monocytes typically make up about 2-8% of your total white blood cells. They act as your body’s clean-up crew to remove damaged cells and help fight bacterial infections. A healthy percentage means your blood contains the expected proportion of monocytes, which are important for normal immune function.
Neutrophils (absolute count) Advanced plan
Neutrophils are the most common type of white blood cell and act as your body’s first line of defense against bacterial infections. A healthy count means your immune system is well-prepared to respond quickly to infection when needed.
Neutrophils (percentage) Advanced plan
Neutrophils are the most common type of white blood cell, typically making up 50–70% of your total white blood cells. They act as your body’s first line of defense against bacterial infections. A healthy percentage means your blood contains the expected proportion of neutrophils, which are important for normal immune function.
White Blood Cell Count
White blood cells are an essential part of your immune system, helping your body fight infections and support healing. A healthy count means your immune defenses are strong and ready to respond in case infection arises.
Systemic Immune-Inflammation Index (SII)
The systemic immune-inflammation index (SII) combines three key blood markers, platelets, neutrophils, and lymphocytes, to reflect the balance between inflammation and your immune defenses. A healthy SII means your immune system is well-regulated, not under excess inflammatory strain, and ready to defend your body against infection effectively.
With lab testing through Hers, you get clear results that span multiple areas of health — connecting the dots between your cardiovascular system, metabolism, hormones, liver, kidneys, nutrients, inflammation, immune function, blood health, stress, and even biological age. The results are explained clearly and simply, so you can easily understand what’s happening inside your body.
Beyond the numbers, Hers provides actionable insights into where you need to focus to improve your health. Each result comes with insights to help you make sense of your biomarkers and identify practical steps to support better outcomes.
If your results suggest areas for improvement, you’ll receive an action plan designed by experts that includes lifestyle guidance and, when deemed appropriate by a healthcare provider, prescription medication to help you reach your goals.
More than 2.4 million people trust Hims & Hers for accessible, science-backed care — from lab testing to ongoing health management.1
Who should get tested for immune health and when?
You may want to consider immune-related blood testing if you:
• Often get infections
• Have unexplained fevers
• Your healthcare provider suspects an immune system issue.
These tests are also commonly used in clinical settings to monitor people taking medications that affect immunity, such as chemotherapy, corticosteroids, or biologic therapies. Testing available through Hers does not replace clinical monitoring or diagnostic testing in such cases.
There is no universal schedule for immune testing in healthy adults. How often you should be tested depends on your symptoms, overall health, and your healthcare provider’s advice. For people with compromised immunity, closer monitoring and preventive strategies, such as updated vaccines, are often recommended.
What does a high white blood cell count mean?
A high WBC count doesn’t always mean infection. It may reflect inflammation, medication effects, smoking, or other medical conditions. Your doctor will interpret results in the context of your symptoms and medical history.
Can lifestyle changes improve immune markers?
Yes. Healthy sleep, a balanced diet, exercise, stress management, and staying current with recommended vaccines all support immune function. Abnormal blood test results should always be discussed with your healthcare provider.
Should I be worried if my lymphocytes or neutrophils are low?
Not necessarily. Temporary changes are common after infections or with certain medications. Persistent or severe abnormalities, however, may require further evaluation to rule out an underlying immune or bone-marrow condition.
What is the Systemic Immune-Inflammation Index (SII)?
SII is a calculation based on blood count components. Studies suggest it may reflect overall immune-inflammatory activity and predict outcomes in some conditions. However, it is still considered a research marker and is not routinely used in everyday medical care for diagnosis.
Can these tests diagnose an immune deficiency?
No. These markers can point to possible issues, but are not enough to diagnose immune deficiencies. If you’re concerned about your results, your provider may order additional, more specialized tests.
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Reviewed by Felix Gussone, MD
Published 11/13/2025
