Health condition
Immunodeficiency testing
Testing the immune system is a staged process matched to the infection pattern: blood counts and immunoglobulin levels first, vaccine response and lymphocyte studies second, genetic and specialised testing where indicated - most usefully orchestrated by an immunologist.
Why trust this guide
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Editorial team
Written by our editorial team from the UK sources listed on each page.
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Sourced from guidance
Checked against current NHS and UK specialist society guidance at the time of review.
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Current for 2026
Reviewed on 2026-09-27 with the next review scheduled for 2027-09-27.
Key facts
The essentials at a glance.
The symptoms to recognise, when to seek help, which specialist to see, and what treatment usually involves.
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Stage 1: full blood count with differential, immunoglobulin levels (IgG, IgA, IgM), serum electrophoresis and HIV testing - identifying most clinically significant adult deficiencies
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Stage 2: specific antibody responses to pneumococcal and tetanus vaccines (testing function, not just levels), IgG subclasses, and lymphocyte subset analysis by flow cytometry
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Stage 3 (specialist-directed): complement studies for recurrent neisserial infection or angioedema, neutrophil function tests for abscesses and unusual organisms, and genetic panels for suspected inborn errors
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Specialist: a consultant immunologist - test selection follows the infection story, and interpretation requires context (age, medications, protein loss and illness all move the numbers)
Understanding the condition
What it is and what happens next.
What causes it, how it is diagnosed, and the treatment routes available in the UK.
What it is and how it feels
Immune testing rewards strategy over shotgun: the infection history writes the request form, because each immune compartment fails in its own dialect - antibody deficiency speaks in recurrent bacterial sinopulmonary infections, complement deficiency in repeated meningococcal disease or unexplained angioedema, neutrophil disorders in abscesses and invasive fungal infection, and T-cell problems in severe viral, fungal and opportunistic illness - and the first-line panel covers the commonest adult territory efficiently: the blood count's neutrophil and lymphocyte numbers, immunoglobulin levels catching the hypogammaglobulinaemias (with electrophoresis to spot the paraproteins that cause them secondarily), and HIV testing, which belongs in every immunodeficiency work-up without exception. Interpretation is where expertise earns its place: immunoglobulins dip with nephrotic protein loss, certain anticonvulsants and rituximab, lymphocyte counts swing with steroids and acute illness, and a borderline IgG in a well person means something entirely different from the same number in someone with bronchiectasis and yearly pneumonia.
Diagnosis and treatment routes
The functional tier answers the question static levels cannot - can this immune system actually perform? - through baseline and post-vaccination antibody titres against polysaccharide and protein antigens (a failed pneumococcal response despite normal total IgG defines specific antibody deficiency, a genuinely treatable diagnosis), flow cytometric mapping of T, B and NK cell populations, and onwards where directed to complement pathway assays, neutrophil oxidative burst testing, and increasingly to genetic panels that have transformed the recognition of inborn errors of immunity presenting in adulthood. The output worth seeking from the whole exercise is a management-grade answer: a named deficiency with its tailored plan - immunoglobulin replacement, prophylactic antimicrobials, vaccination strategy adjustments, family screening where inherited - or a documented clean bill that redirects attention to the structural and environmental amplifiers of infection, either outcome being worth considerably more than the untested uncertainty it replaces. In many parts of the UK, routine NHS referrals for this kind of problem currently take 20-45+ weeks, whereas an initial appointment with a private consultant is typically available within around two weeks.
Seeing a specialist
Who to see, and how quickly you can be seen.
The specialist for this condition is usually a consultant immunologist. Your GP can refer you on the NHS, or you can arrange a private consultation directly.
A quiet reminder
This guide is for information, not medical advice.
Your GP knows your history and can tell you which parts apply to you. If in doubt, see them - and seek urgent care for any of the emergency symptoms described above.
Frequently asked
Common questions about Immunodeficiency testing.
Quick, plain-English answers to what people ask us most.
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Can you explain what Immunodeficiency testing is?
Immunodeficiency testing is a health condition that affects how part of the body functions, and can range in severity from mild to significant depending on the individual. A clinician can assess your specific situation and explain what it means for you. Understanding the basics helps you ask the right questions at your appointment.
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Why does immunodeficiency testing happen?
There are usually several contributing factors behind immunodeficiency testing, and it's not always possible to pin down a single cause without proper assessment. Your doctor will consider your symptoms, history, and any relevant investigations to build a clearer picture. This helps make sure treatment is targeted appropriately.
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What are the symptoms of immunodeficiency testing?
Symptoms can vary from mild and barely noticeable to more significant and disruptive, depending on severity and individual factors. Common features often include changes that affect comfort, function, or general wellbeing in the affected area or system. If you're experiencing symptoms that concern you, it's worth having them assessed rather than guessing.
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How worried should I be about immunodeficiency testing?
Most cases can be managed effectively once properly assessed and treated, though how serious it is depends on individual circumstances and how early it's picked up. Getting a professional opinion helps rule out anything more concerning and puts your mind at ease either way. Don't hesitate to seek advice if something feels wrong.
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Is immunodeficiency testing hereditary or genetic?
Some cases have a genetic or family component, while others are linked more to lifestyle, environment, or other health conditions. Having a family history may increase your risk slightly, but it doesn't mean you'll definitely develop it. A clinician can advise whether genetic factors seem relevant in your particular case.
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Can immunodeficiency testing be treated or reversed?
Treatment can often reduce symptoms significantly and, in some cases, resolve the underlying problem entirely, though this isn't guaranteed for everyone. Prevention strategies, where they exist, usually focus on managing risk factors and general health. A tailored discussion with your doctor will give you the clearest picture for your circumstances.
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How is immunodeficiency testing treated?
Treatment options range from conservative measures such as lifestyle changes, medication, or physiotherapy through to more involved interventions in more severe or persistent cases. The right approach depends on the underlying cause, severity, and how it's affecting you. Your specialist will talk through the pros and cons of each option that's relevant to you.
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What is the typical recovery time for immunodeficiency testing?
Some people recover within a matter of weeks, while others find it becomes a longer-term or recurring issue that needs ongoing management. Following your treatment plan closely tends to support the best possible recovery. Ask your specialist for a realistic timeline based on your own results and progress.
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When is a specialist opinion or surgery needed for immunodeficiency testing?
A specialist opinion is generally recommended if symptoms persist despite initial treatment, if they're severe, or if there's uncertainty about the diagnosis. Surgery or more invasive treatment is usually reserved for cases where conservative measures haven't worked. Your GP can refer you on if they feel a specialist review would be helpful.
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When should I see a doctor about immunodeficiency testing?
See a doctor if symptoms are persistent, worsening, or affecting your daily life, or sooner if you have any red-flag symptoms your GP has warned you about. Waiting times through the NHS often run to 20-45+ weeks for a routine referral, whereas a private specialist can usually see you within roughly 2 weeks.