Ask a Doctor: How do I know the state of my immune system?

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Q: How do I know the state of my immune system? Can I get it tested, and how do I support it?

A: It’s normal to catch a few run-of-the-mill infections every year. That may include two to three colds, an occasional bout of food poisoning (1 in 6 people in the United States get a foodborne illness each year), and possibly the flu or covid-19. If that sounds like you, then testing specific cells of the immune system likely won’t provide any useful information. Instead, you can take steps to support your overall health and immune system.

But if you get sick often – with four or more infections per year that require antibiotics, for example – you should talk to your physician about running tests to determine whether you have a health condition that’s impacting your immune system. Certain disorders, including genetic ones, affect your ability to fight infections, and conditions like diabetes can weaken immunity.

Here’s how you can support your immune system, as well as what to know about testing and conditions.

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Supporting your immune system

Be wary of any supplements or probiotics that promise to improve your body’s ability to fight infection. Research has shown that these are not actually the quick fixes we’d all love them to be.

Getting routine vaccines. Staying up-to-date with your vaccinations is the best thing you can do for your immune system.

Eating healthy. A balanced diet can help ensure you’re meeting nutritional needs. A variety of fruits, vegetables and whole grains contain the key vitamins and nutrients that are important for your immune system.

Prioritizing physical activity. Moderate exercise has been shown to boost immune cell activity. Aim for about 150 minutes of physical activity per week.

Getting a good night’s rest. Sleep loss has a powerful effect on our immune system’s functioning – including hampering antibody production. Most adults need seven or more hours per night.

Reducing stress. Chronic stress causes your body to release the hormone cortisol, which can reduce your body’s white blood cells, raises your risk of upper respiratory infections and increases the amount of time it takes for wounds to heal. Try short, meditative breathing exercises to help cope.

Quitting smoking and cutting down alcohol. Nicotine and cigarette smoke suppress the immune system, as does alcohol. Your doctor can help you with resources, including medications, to help you break a habit.

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Testing your immune system

Your immune system protects you against bacteria, viruses and other potentially harmful foes. Among its soldiers are white blood cells, known for their ability to find and kill invaders, and plasma cells, which produce antibodies.

A critical defect in the immune system can make you immunocompromised, a term often used interchangeably with immunodeficient.

If you get sick more than usual, your immune system may be deficient, and further testing may determine a diagnosis. Doctors often start by looking at your overall antibody levels, or immunoglobulins, and a complete blood count to check your white blood cell levels. In some cases, we may need to perform advanced tests – like flow cytometry, which uses lasers to analyze cells – to identify the exact molecular issue or analyze your genome to find mutations.

Depending on your history, additional tests for conditions like chronic kidney disease, such as a urinalysis or comprehensive metabolic panel, can be useful to uncover other reasons you may be immunodeficient.

It may also help to test for antibodies to specific infections. While the majority of the U.S. population has developed antibodies to covid-19 by now – and testing for those antibodies isn’t particularly helpful – this is not the case for less common infections.

When evaluating some diseases such as hepatitis, testing for specific antibodies is routine. They can clue your doctor into the possibility of an active infection and can give them information about how your immune system is responding.

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Conditions that impact your immune system

Some genetic conditions – such as common variable immune deficiency or selective IgA deficiency – impair the body’s ability to produce effective antibodies in general.

Immunocompromising diseases include HIV, which depletes certain white blood cells and can leave people vulnerable to life-threatening infections. If you’re in a higher risk group, such as men who have sex with men or injection drug users, don’t delay talking to your physician about getting started on pre-exposure prophylaxis (PrEP).

Autoimmune conditions, on the other hand, occur when the immune system mistakenly creates antibodies against its own body. Autoimmune conditions themselves don’t make people fully immunocompromised, but they’re commonly treated with immune-suppressing drugs that cause people to become so.

Also, people with certain health conditions are at higher risk of getting sick. These situations include:

– Diseases like cirrhosis, chronic kidney disease and diabetes.

– Old age. Our immune system tends to decline with age, and those over 65 often become sicker when infected.

– Going through chemotherapy or taking other medications that suppress the immune system. In these scenarios, your physician may already be monitoring your blood counts.

– Pregnancy. While not immunocompromising, per se, pregnancy is associated with unique alterations in the immune system that can make you vulnerable to infections.

In cases like these, additional testing of the immune system won’t necessarily provide you with helpful information. Nonetheless, you may need to be more careful about preventing an infection by wearing a mask in crowded spaces, for example.

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Trisha S. Pasricha is a physician at Massachusetts General Hospital, an instructor in medicine at Harvard Medical School, and a medical journalist.

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