What Weakens Immunity & How To Support The Immune System

woman with a weakened immune system

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This Article was originally published on Rupa Health. *

We all learned quickly through the COVID-19 pandemic the importance of protecting and supporting the immune system. There have been 6.9 million deaths associated with the virus around the world since the beginning of the outbreak in January 2020. Viruses aren’t the only threat to our health. It’s estimated that bacteria cause 7.7 million deaths globally every year.

A robust immune system is necessary for protecting the body from these pathogens. This article will explain the immune system, symptoms and causes of lowered immunity, tests for identifying a root cause for lower immunity, and a functional medicine immune support protocol.

What is The Immune System?

The immune system is our body’s primary defense system. It comprises an intricate network of cells and organs that protect you from pathogens, like bacteria, viruses, fungi, and parasites, and harmful changes inside the body, such as cancer cells.

Your immune system’s first line of defense against germs is the skin and mucous membranes. Oils and immune cells are secreted onto the skin to prevent these pathogens from getting into the body. Mucous membranes help trap, destroy, and remove germs.

Once pathogens have entered the body, various glands mount a defense to attack and kill them. The tonsils and the adenoids are in the throat and nasal passage region to stop and destroy pathogens in this area. Lymph nodes are located all throughout the body and filter and kill germs to prevent them from spreading. The spleen, located in your abdomen, filters out damaged red blood cells and makes and stores germ-fighting white blood cells. The thymus gland is a gland located in your upper chest and matures white blood cells into a type of immune cell called a T-lymphocyte that defends against pathogens and even cancer cells.

White blood cells are vital to the immune system as they search for and destroy pathogens entering the body. Numerous types of white blood cells protect the body from germs and cancer cells in various ways. These cells communicate with other parts of the immune system to mount a defense against the disease or infection.

A particular type of white blood cell also produces immunoglobulins, or antibodies, which are molecules that play a critical role in your immune system. They recognize and bind to specific antigens, such as bacteria and viruses, to signal other immune cells that they must be destroyed.

pathogens such as bacteria and viruses

Your gastrointestinal system also plays a crucial role in your immune system. Your stomach secretes stomach acid, which helps kill germs when they enter. The intestines contain immune cells in the mucosal layer and the gut lining. The trillions of microorganisms that comprise the gut microbiome play an essential role in our immune defense.

Now that you know about the cells and organs that make up the immune system, let’s talk briefly about how this system works. The immune system is made up of the innate (non-specific) and the adaptive (specific) immune systems.

The innate immune system mounts a rapid, general defense against harmful pathogens and cells by identifying and destroying them. The adaptive immune system mounts a slower response but is more specific by making antibodies against a specific germ. Then the next time your body comes in contact with this germ, your immune system immediately recognizes it and can eliminate it efficiently.

When problems arise to suppress the immune system, it leads to under activity, which increases your susceptibility to infection and cancer. When the immune system is overactive, on the other hand, we see issues like allergies and autoimmunity. In the remaining sections of this article, we will focus on the problems arising from the under activity of the immune system in the defense against pathogens.

Symptoms of Lower Immune System

When the immune system is weakened, you have more difficulty fighting off pathogens and are more susceptible to infections. Symptoms of a lower immune system include:

  • Frequent infections (bacterial, viral, or fungal)
  • Infection or illness that lasts longer than usual or is difficult to treat
  • Fatigue, even when you get enough sleep
  • Fever
  • Weight loss
  • Diarrhea or constipation
  • Nausea
  • Loss of appetite
  • Low White Blood Cell or platelet counts on lab work
  • Inflammation in the body
woman with a weak immune system

What Causes Lower Immune Systems?

Various biological and environmental factors can cause a lower immune system. Some things that are a natural part of life, such as pregnancy and aging, are associated with a weaker immune response.

Genetics can cause inherited conditions associated with a weakened immune system, called immunodeficiency disorders.

Certain medications for treating cancer, autoimmune diseases, and organ transplants suppress the immune system. This includes chemotherapy, steroid medications, and methotrexate, among others.

Various illnesses weaken the immune system. These include cancer, diabetes, HIV, major burns, and infections like influenza and mononucleosis.

Malnutrition and micronutrient deficiencies, such as vitamin A, vitamin B6, vitamin B12, folate, vitamin C, vitamin E, copper, magnesium, selenium, and zinc, can weaken the immune system. Vitamin D is also associated with an increased susceptibility to infections.

The gut microbiome plays a vital role in the immune system. An imbalance in the microbiome, called gut dysbiosis, is associated with various immune complications, including increased susceptibility to infections.

Alcohol disrupts immune function in several ways, including disrupting the function of immune cells in the respiratory system and the barrier function in the cells that line the lower airways. Alcohol also disrupts immune function via its impact on the gut. Alcohol disrupts the gut microbiome, damages immune cells in the gut, and increases intestinal permeability (also called “leaky gut“), negatively impacting the immune system.

Other lifestyle factors that weaken immune function and lower immunity over time include physical inactivitysleep deprivation, and chronic stress.

woman who is sleep deprived and stressed

Functional Medicine Labs to Test for Root Cause of Lower Immunity

If you’re struggling with frequent and difficult-to-treat infections, fatigue, or any other symptoms of a weakened immune system, after ruling out pregnancy, your functional medicine practitioner will also order basic blood work to identify a root cause for your lower immunity.

Complete Blood Count (CBC)

CBC with differential is a standard blood test that provides a total white blood cell count and the differential identification of 5 types of white blood cells: neutrophils, lymphocytes, monocytes, eosinophils, and basophils. A CBC also measures the size and number of red blood cells, number of platelets, and other parameters to provide a general indication of overall health status.

Comprehensive Metabolic Panel (CMP)

CMP is another standard blood test that provides information on overall health status. This test measures blood glucose levels, kidney and liver function, metabolism, and electrolyte balance, which can indicate other conditions or factors impacting your health that could impair immune function.

Total Immunoglobulins

Measuring total immunoglobulins (IgG, IgM, and IgA) provides insight into whether your immune system is struggling to produce these essential immune molecules, which would indicate a weakened immune defense.


When the immune system is challenged, it triggers inflammation. Testing for markers of inflammation, such as CRP and ESR, can provide helpful insight that allows for a more targeted treatment protocol.

Functional Medicine Labs That Can Help Individualize Immune System Support Protocol

Comprehensive Stool Test

Since 70-80% of the body’s immune cells reside in the gut, assessing gut health can provide valuable insight into immune health. The GI-MAP + Zonulin provides valuable insight into the health and function of the gastrointestinal system, such as digestion, absorption, and microbiome health. The addition of zonulin to this test provides information on intestinal permeability or leaky gut. Most stool tests also assess Secretory IgA, an immunoglobulin important for immune health.

Micronutrient Testing

Several micronutrients play vital roles in the immune system, and deficiencies in these nutrients can weaken the immune system. In patients with a weakened immune system, a Micronutrients Panel can offer insight into their nutrient status, allowing the practitioner to create a targeted treatment plan for optimal immune support.

Vitamin D is included in the micronutrients panel but can be performed as part of standard comprehensive blood work.

Specific Pathogens

Your functional medicine provider may test for specific bacteria or viruses, such as Epstein Barr Virus, which causes mononucleosis. A comprehensive panel that evaluates seven different opportunistic infections, including Epstein Barr Virus, can be performed with the Vibrant Wellness Opportunistic Infections panel.

green juice and a napkin that says boost your immune system

Functional Medicine Treatment Protocol To Boost Immunity

A functional medicine treatment protocol to boost immunity must first and foremost address the lifestyle factors that may impair immune function. Avoiding alcohol, increasing physical activity, getting adequate quality sleep, and managing stress are vital for a robust, healthy immune system.

Therapeutic Diet and Nutrition Considerations to Boost Immunity

An anti-inflammatory, nutrient-dense, high-fiber diet is optimal when it comes to nutrition considerations to boost immunity. This eating style supports a healthy gut and microbiome, which is extremely important for immune health. A Mediterranean Diet is a therapeutic eating pattern that encompasses these goals well.

Mediterranean Diet is a high-fiber, anti-inflammatory diet rich in nutrients. Seasonal fruits and vegetables, herbs, legumes and beans, whole grains, and healthy fats, particularly olive oil, are all components of a Mediterranean diet. Poultry, seafood, eggs, and dairy are consumed in moderation; however, the emphasis is on high-fiber plant foods.

In addition to supporting a healthy gut microbiome, a Mediterranean diet boosts immunity by reducing inflammation, activating immune cells, and reducing the risk for conditions known to weaken the immune system, such as type 2 diabetes and cardiovascular disease.

Supplements Protocol to Boost Immunity

A functional medicine supplements protocol to boost immunity takes a patient-centered, individualized approach. Your unique lifestyle, environmental factors, and basic and specialty laboratory testing results are considered when tailoring a treatment plan unique to your needs. The following supplements are commonly prescribed for boosting immunity; however, it’s essential to follow your health practitioner’s guidance to ensure you’re taking supplements that are right for you.

NOTE: the links to all supplements listed below will take you to our secure online supplement store where you can purchase professional grade quality supplements after creating a secure login.

Multivitamin Multimineral Supplement

A broad base of vitamins and minerals can be obtained from a high-quality multivitamin multimineral supplement to support optimal immune health. The Designs for Health DFH Complete Multi™ with Copper is an example of a quality multivitamin multimineral that contains immune-supportive micronutrients, such as vitamin A, vitamin B6, vitamin B12, folate, vitamin C, vitamin D, vitamin E, copper, magnesium, selenium, and zinc.

The following is the recommendation for DFH Complete Multi™ with Copper; however, always follow the advice of your healthcare practitioner.

Dose: 2 capsules with lunch and dinner

Duration: Ongoing


L-glutamine is an amino acid used throughout the body and is especially important for gut health as it provides the fuel source for the cells that line the intestines. Factors including stress and alcohol consumption cause an increase in inflammation and damage to the gut lining, increasing gut permeability, which weakens the immune system. L-glutamine reduces gut inflammation and supports healing of the gut lining, reducing intestinal permeability. Clinical studies show that supplementing with L-glutamine boosts immunity and decreases infections.

Dose: 5 grams 3 times per day, taken on an empty stomach

Duration: 8 weeks


Probiotics are strains of bacteria that have beneficial effects on human health. Probiotic supplements offer support for a healthy gut microbiome and boost immunity. Probiotics boost immunity by improving gut barrier function, maintaining a healthy gut lining, stimulating protective responses from the intestinal lining against pathogens, and modulating inflammation.

An example of a high-quality probiotic is Ortho Molecular Products Ortho Biotic, which contains six strains of beneficial bacteria and one strain of beneficial yeast, providing 23 billion colony-forming units (CFU) of probiotic support.

Dose: 1 capsule per day, with meals

Duration: Ongoing

Vitamin C

Vitamin C, also referred to as ascorbic acid, is an essential vitamin for optimal health. It is an antioxidant involved in several biological processes and profoundly impacts immune health. Vitamin C boosts immunity by impacting barrier integrity and modulating white blood cell function. Studies show that when patients with recurrent infections were supplemented with Vitamin C, there was a significant improvement in the antibacterial action of neutrophils, a type of White Blood Cell.

This is a common recommendation for vitamin C for an adult.

Dose: 250 – 500 mg twice per day

Duration: Ongoing

Immunitone Plus

Immunitone Plus™ is an immune support formula containing several common immune-boosting herbs, such as echinacea, astragalus, elderberry, green tea extract, and several types of mushrooms.

Echinacea may help protect against catching a cold. Astragalus is an herb with antibacterial and anti-inflammatory properties and is also shown to protect against colds and upper respiratory infections. It is also known as an adaptogen herb, which helps the body better adapt to stress. Elderberry is known to be packed with antioxidants and vitamins that can reduce inflammation and support the immune system. Green tea leaves are full of antioxidants, and this herb has been shown to modulate innate and adaptive immune systems and intestinal immunity. Mushrooms have antimicrobial and anti-inflammatory properties and modulate the immune system by affecting various immune cells.

The following is the recommendation for Immunitone Plus™; however, always follow your doctor’s advice. This supplement is not recommended for pregnant or lactating women.

Dose: 4 capsules per day with meals

Duration: ongoing for immune support

Vitamin D

Vitamin D provides a variety of benefits for overall health. It reduces inflammation, regulates glucose metabolism, and modulates innate and adaptive immune responses. As stated in this article, vitamin D deficiency is associated with increased susceptibility to infection, and evidence indicates that supplementing with it may protect against infection. A prospective, double-blinded placebo study found that Vitamin D supplementation reduced the incidence of influenza infection by 42%. As you can see, vitamin D is a vital nutrient to test and optimize for healthy immune function.

To raise blood levels of Vitamin D to normal ranges, a “loading dose” is typically required.

Loading Dose: 50,000 IU 3 times per week

Duration: 1 month

After normal blood levels are achieved, a maintenance dose is needed to maintain optimal Vitamin D levels.

Maintenance Dose: 800 to 2,000 IU of Vitamin D3 per day

Duration: Ongoing

In any protocol, it’s necessary to consider the total amounts of nutrients from all supplementals. For example, the multivitamin in this protocol contains 1,000 IU of vitamin D3. After the loading dose of vitamin D boosts levels to normal ranges, this multivitamin may satisfy the daily vitamin D3 requirement. Monitoring blood levels of vitamin D with laboratory testing will dictate whether the multivitamin contains enough vitamin D to maintain normal levels or whether an additional vitamin D3 supplement is necessary.

woman holding her arms up making muscles representing a strong immune system

When to Retest Labs

When infection is present, retesting basic blood work in 2 to 4 weeks is ideal for monitoring the effectiveness of treatment.

It is best to wait 3 to 6 months before retesting Vitamin D levels after beginning Vitamin D supplementation.

Retesting a comprehensive stool analysis and micronutrient panel in the 3 to 6 months time frame is also ideal for providing adequate time for the treatment protocol to improve the nutrient status and gut health.


Your immune system is what protects your body from pathogens. It’s working hard every day to prevent germs from entering your body and keep you healthy.

There are lots of things that can be done to support your immune system. Eating healthy, getting quality sleep, managing stress, and physical activity are foundational ways to boost your immunity.

If you feel your immune system is weakened, talk to your functional medicine provider about functional lab work to identify a root cause and supplements to help your immune system heal.

Immune System Support: Gut Health, Mushrooms, & More!

Gut health plays a major role in overall immune health. Keeping your gut healthy is a great way to boost immunity. Here are a few articles with gut support tips:


Mushrooms contain active compounds that are immune boosting powerhouses! For more information on how to use mushrooms to boost immunity check out this article!

You can learn more about other wellness practices that support immunity with these articles:

Note: If you buy something through our links, we may earn an affiliate commission, at no cost to you. We only recommend products we genuinely like. Thank you for your support!

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