Immune System Test: How do I know if my immune system is weak?
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Overview
It’s normal to catch a cold when the seasons change. But if you are constantly fighting off bugs or taking weeks to recover, you might be worried about your immune defences.
While there is no single test that gives you an “immunity score,” Australian doctors use specific pathology tests and your medical history to assess your immune health.
Signs
Your body usually gives clear signals when it is struggling to keep up with infections.
Frequent infections
Adults averaging more than four colds a year, or needing multiple courses of antibiotics, may have an underlying issue.
Slow recovery time
If a simple three-day virus knocks you around for two weeks, your immune defence system may be sluggish.
Constant fatigue
Feeling exhausted even after adequate sleep is common, as your body uses energy to fight low-level inflammation.
Digestive issues
Frequent digestive problems such as bloating or diarrhoea can be a warning sign, as much of the immune system is located in the gut.
Slow-healing wounds
Minor cuts or grazes that linger for weeks without healing can indicate a delayed immune response.
Note: Stress and burnout often mimic these symptoms. Always see your online GP to rule out lifestyle-related causes first.
Causes
Immune issues usually stem from lifestyle factors or underlying medical conditions.
Nutritional deficiencies
A lack of essential nutrients such as zinc, iron, or vitamin C can prevent immune cells from functioning properly.
Chronic stress and sleep loss
Persistently high cortisol levels (the stress hormone) suppress the immune system, increasing susceptibility to infections.
Secondary immunodeficiency
This form of immune weakness is acquired from external factors such as medications (steroids or chemotherapy), chronic illnesses like diabetes, or certain viral infections.
Primary immunodeficiency
These are rare genetic conditions present from birth where parts of the immune system are absent or do not function correctly.
Tests to Check
Doctors use standard pathology labs to check the basics first.
Full Blood Count (FBC)
This is the standard starting point for most medical investigations.
It counts your white blood cells, which are the primary soldiers that fight infection.
Immunoglobulin Levels
This test measures the proteins (antibodies) in your blood that recognise germs.
Low levels suggest your body may struggle to remember and fight off specific bacteria or viruses.
Vitamin and Mineral Screen
Nutritional gaps are a leading cause of poor immunity in Australia.
GPs commonly check iron, vitamin D, and vitamin B12, as deficiencies can suppress immune function.
Tests That Assess Immune Strength
| Test | What it checks | Why it matters for immunity |
| Full Blood Count | White blood cell numbers (neutrophils/lymphocytes) | Low cells mean weak defence; high cells suggest active infection |
| Immunoglobulins | Antibody levels (IgG, IgA, IgM) | Low antibodies create “blind spots” in defence against germs |
| CRP (C-Reactive Protein) | Inflammation markers | High levels suggest the body is chronically fighting infection |
| Vitamin D | Stored vitamin D levels | Vitamin D activates immune cells; low levels are common in office workers |
| Vaccine Response | Antibodies to past vaccines (e.g. tetanus) | Checks whether the immune system can “learn” from vaccines |
Treatment Depends on the Cause
“Weak immunity” is a result, not a disease. Treatment focuses on fixing the underlying trigger.
Lifestyle changes
Prioritising sleep, reducing alcohol intake, and managing stress are the most common treatments recommended.
Supplements
If blood tests confirm a deficiency (such as vitamin D), targeted supplements can restore immune function effectively.
Medication adjustment
If prescribed medications are suppressing your immune system, your doctor may adjust the dose or change the medication.
Specialist therapies
For genetic immune disorders, patients may require immunoglobulin replacement therapy (donor antibodies) via IV infusion.
How Can an Online Doctor Help?
Online GPs and telehealth services can assist with immune system testing in several ways.
Telehealth consultation: An online doctor can assess your symptoms, medical history, and lifestyle factors that affect immunity, and advise whether testing is needed.
Test referrals: If clinically appropriate, an online GP can issue pathology referrals for tests such as white blood cell counts, immunoglobulin levels, or other immune function tests.
A referral can be requested via a telehealth appointment.
Interpretation of results: Once your tests are completed, a web doctor can explain the results and identify areas of concern.
Follow-up care: Based on results, doctors may recommend lifestyle changes, supplements, or medications to support immune health.
Convenience: Telehealth allows you to manage your health remotely, reducing the need for unnecessary clinic visits.
FAQ
Can you check your immune system with one test?
No. A single test does not provide the full picture. Doctors typically run a panel of tests to assess white cells, antibodies, and inflammation.
Are immune system tests bulk billed in Australia?
Yes. Standard tests like FBC and immunoglobulin levels are usually bulk billed under Medicare when ordered for a valid clinical reason.
Can you get immune tests through telehealth?
Yes. A telehealth doctor can email a pathology request form that you can take to any local collection centre.
Does low vitamin D mean low immunity?
Vitamin D plays a major role in activating immune cells. Deficiency is common in Australia and is linked to increased infections.
How long do results take?
Basic blood tests usually return results within 24–48 hours. More complex tests, such as vaccine response checks, may take up to a week.
Can supplements boost immunity?
Supplements help only if you have a confirmed deficiency. Taking extra supplements without a deficiency will not strengthen immunity further.
Is There a Single Test for a Weak Immune System?
No. The immune system is complex, so doctors use a staged approach rather than relying on one test.
Your GP will usually start with a physical exam and review of your infection history, then order a combination of blood tests if needed.
How do doctors diagnose immune system issues?
Diagnosing immune problems involves careful assessment and investigation.
Medical history: Your doctor will ask about symptoms, infection frequency, family history, lifestyle, and medications.
Physical examination: This includes checking for signs of infection, inflammation, or swollen lymph nodes.
Targeted testing: Based on findings, doctors may order blood tests or other investigations to identify the underlying cause.
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Disclaimer
This blog is for general informational purposes only and does not indicate that Hola Health provides all treatments or preventive measures mentioned. It is not intended to be a substitute for professional medical advice. Always seek the guidance of your doctor or other qualified health professional with any questions you may have regarding your health or a medical condition. For emergencies please immediately contact 000. Any medical topics discussed are intended to educate, not to imply availability through Hola Health.