Immune system blood tests (Immunological investigations (immune function blood tests))
A set of blood tests a clinical immunologist may use to find out whether your immune system is working normally, usually when infections are unusually frequent, severe or hard to shift.
✓ Medically reviewed by a GMC-registered consultant · last reviewed September 2026 · next review September 2027 · how we review
In short
- This is a panel of different blood tests, chosen by a specialist to answer a specific question — not one single 'immune test'.
- A blood result alone is not a diagnosis: abnormal or borderline results need specialist interpretation alongside your symptoms and history.
- Some results come back in days, but vaccine-response checks and confirmatory retests can take several weeks.
- Frequent ordinary infections are common and usually mean a normal immune system; testing without a clear reason can cause needless worry.
A plain-English summary. The detail — including risks and recovery — is below.
At a glance
A general guide. Your specialist will give you advice for your situation.
Can identify a treatable antibody deficiency or other immune problem behind recurrent or serious infections
Broad immune screening is the wrong approach for vague tiredness or run-down feelings without a clear infection or autoimmune pattern.
Blood is taken from a vein, usually in a few minutes. You can eat, drink and carry on as normal unless told otherwise.
A named clinician — ideally a consultant immunologist — responsible for interpreting and explaining results.
Blood is taken from a vein, usually in a few minutes. You can eat, drink and carry on as normal unless told...
Press on the site for a minute or two. Mild bruising is normal. You can drive and return to work straight away.
Basic antibody, complement and blood count results often return within a few days.
If vaccine-response testing is needed, you return for a repeat blood test a few weeks after the vaccine.
What are immune system blood tests?
Immune system blood tests are a group of blood tests that look at different parts of your immune system. They are not a single test. Depending on the question, a clinical immunologist might check your antibody (immunoglobulin) levels, how well you respond to vaccines, your complement proteins, your immune cells, or antibodies that act against your own body.
These tests are usually arranged when something specific needs explaining — for example, infections that keep coming back, are unusually severe, or are caused by unusual germs. They are also used to look into possible autoimmune conditions, where the immune system mistakenly targets the body's own tissues.
It is important to understand what these tests can and cannot do. They can show whether part of the immune system is missing, low or overactive. They cannot, on their own, tell you why you feel unwell, and they will not pick up every problem. A result only makes sense alongside your symptoms, your history and an examination by a clinician.
Many people with frequent everyday infections — coughs, colds, sore throats — have a completely normal immune system. Testing is most useful when there is a genuine pattern that a specialist thinks is worth investigating, rather than as a general 'MOT' for tiredness or run-down feelings.
Types, options & approaches
There may be different ways to do this. The right approach depends on the clinical question and your circumstances.
Antibody levels vs vaccine response testing
| Antibody levels | Vaccine response | |
|---|---|---|
| What it shows | How much antibody you have | Whether antibody actually works |
| Single visit? | Usually yes | No — before and after a vaccine |
| Time to result | Days | Several weeks |
| Best for | Spotting low or high levels | Spotting a faulty response when levels look normal |
These tests answer different questions and are often used together. Your immunologist decides which are needed.
Preparing for your test
- Bring a clear timeline of your infections: how often, how severe, which antibiotics or hospital visits were needed, and any unusual germs identified.
- Bring a full list of your medicines and supplements; some (such as steroids and certain immune-suppressing drugs) affect results.
- Mention any family history of immune problems, frequent serious infections or autoimmune disease.
- Bring copies of previous blood results if you have them, to avoid repeating tests.
- Tell the team if you are pregnant or might be, or if you have recently had a vaccine or infection.
- Ask which specific tests are being done and what each one is for, so you know what to expect.
- Allow time — some answers depend on a follow-up vaccine and a repeat blood test weeks later.
What happens
An immunologist or your referring doctor takes a history and examines you, then chooses which blood tests are needed. A nurse or phlebotomist takes one or more blood samples from a vein in your arm, usually at a single visit.
Different samples go to different parts of the laboratory. Simple antibody and complement levels may come back within days. Vaccine-response testing is done in stages: a baseline sample, a vaccine, then a second sample several weeks later to see how your body responded.
When results are back, the immunologist interprets them together — not in isolation — alongside your symptoms and history. Some results are borderline or need repeating, because levels naturally vary over time.
Is this test right for me?
A good consultation should explore whether it's the right choice for you now — including reasons to wait or consider something else.
May not be suitable if…
- Broad immune screening is the wrong approach for vague tiredness or run-down feelings without a clear infection or autoimmune pattern.
- Testing during an acute infection or shortly after a vaccine can give misleading levels.
- If you are on steroids or immune-suppressing drugs, results may reflect the medicine rather than your underlying immune system.
- If symptoms point clearly to another cause (for example iron deficiency or stress), that should be addressed first.
- Self-requested 'immune panels' without specialist guidance often cannot be safely interpreted.
Delay or rearrange if…
- You currently have an active infection or have just recovered from one.
- You have had a vaccine in the last few weeks (unless the test is the planned response check).
- You are taking steroids or immune-suppressing medicines that have not been discussed with the team.
- Pregnancy or another temporary factor may distort results — check with your clinician.
- Previous results are not yet available and could avoid repeat testing.
Alternatives to discuss
- No testing, if there is no clear pattern and symptoms are mild — watchful waiting with a clear plan.
- Addressing common, treatable causes first, such as iron deficiency, poor sleep or stress.
- A standard NHS pathway via your GP, who can do first-line tests and refer if needed.
- A focused single test rather than a broad panel, guided by your specific problem.
- Specialist immunology assessment to decide whether any testing is warranted at all.
Before you decide
Use this as a shared-decision checklist. The aim is not just “can this be done?”, but whether it is right for you, now, with the risks and alternatives clearly understood.
What matters most to me?
Think about symptoms, daily life, work, caring responsibilities, sport, fertility, travel, appearance and anxiety — the right choice depends on your priorities, not just the medical facts.
What are all my options?
Ask about waiting, monitoring, medicines, rehabilitation, a smaller or larger procedure, a different test, NHS referral, or a second opinion where that would help.
What would make me pause?
Active infection, pregnancy, unstable medical problems, smoking, medicines that increase bleeding, poor support at home, or feeling pressured are all reasons to slow down and get tailored advice.
What happens if I do nothing today?
For some problems, waiting is safe; for others, delay can make treatment harder. A good consultation should explain the trade-off in plain English.
Benefits
- Can identify a treatable antibody deficiency or other immune problem behind recurrent or serious infections
- Can help confirm or rule out an autoimmune condition as part of a wider assessment
- Can guide whether you need vaccines, preventive antibiotics or referral to a specialist centre
- A normal, well-chosen set of results can be reassuring and help avoid unnecessary further tests
- Helps direct treatment to the right problem rather than guessing
Risks & complications
- Minor bruising, soreness or a small lump where blood was taken
- Borderline or mildly abnormal results that need repeating
- Anxiety while waiting for results or interpretation
- Finding something unexpected that needs further (sometimes unnecessary) investigation
- Feeling faint during or after the blood test
- A result that is hard to interpret and leaves uncertainty
- Being labelled with a 'deficiency' that may not actually cause your symptoms
- Infection at the needle site
- A misleading result that delays the correct diagnosis if acted on without specialist input
The biggest pitfall is over-testing: ordering broad immune panels without a clear reason often produces borderline or incidental findings that cause worry without changing care. Ask which tests are genuinely needed, what each result would change, and who will interpret abnormal results — this should be a clinical immunologist, not the test report alone.
Published figures to discuss
These are low-risk blood tests, so there are no meaningful 'complication rates' in the surgical sense. The important numbers relate to interpretation: how often results are borderline, false positives in autoantibody tests, and how often broad testing turns up incidental findings. These vary widely with the population tested and which tests are ordered, so exact figures are not quoted here.
| Figure | Reported range | How to interpret it | Source / confidence |
|---|---|---|---|
| Mild lymphocyte, neutrophil or immunoglobulin abnormality that normalises on repeat | Common | Recent infection, steroids and laboratory variation can affect screening blood tests. | Newcastle Hospitals NHS — Clinical immunology and allergy referral guidelinesnewcastle-hospitals.nhs.ukSource-linked context |
| Secondary immune deficiency | Commoner than many primary immune deficiencies | Medicines, blood cancers, kidney or gut protein loss and HIV should be considered where relevant. | Guide sourcesClinical context |
| Serious primary immune deficiency presenting in adulthood | Uncommon, but important | Recurrent pneumonia, bronchiectasis, unusual infections or poor vaccine responses justify specialist work-up. | Newcastle Hospitals NHS — Clinical immunology and allergy referral guidelinesnewcastle-hospitals.nhs.ukSource-linked context |
| False reassurance from one normal screening panel | Possible | Functional antibody testing and trend over time may matter more than a single normal count. | Guide sourcesClinical context |
These are literature figures, not a personalised prediction. Your own risks and likely benefits depend on your circumstances, your health, and how your care is carried out and followed up.
What happens afterwards
There is no physical recovery from having blood taken. 'Afterwards' is mainly about waiting for results and understanding what they mean for you.
- A small bruise or tender spot where blood was taken
- No change in how you feel — the test itself does not treat anything
- Waiting, sometimes for weeks, before the full picture is clear
- Being asked to repeat a test because levels vary over time
- Some results coming back normal even though you still have symptoms
Aftercare
- Keep the small dressing on for an hour or so and avoid heavy lifting with that arm briefly if it is sore.
- Make a note of when and how you will get your results.
- Do not change or stop any medicines based on a result until a clinician advises you.
- If asked to come back for a vaccine-response retest, keep that appointment — the test is incomplete without it.
- Bring your questions to the results appointment, especially 'what will this change?'
- If you are told a result is borderline, ask whether and when it should be repeated.
- Keep a copy of your results for future reference and to avoid duplicate testing.
- Infection timeline written down
- Medicine and supplement list ready
- Previous blood results gathered
- Family history of immune or autoimmune problems noted
- Clear note of how results will be communicated
- Follow-up vaccine-response appointment booked if needed
- List of questions for the results discussion
⚠ Get urgent help if…
- A high temperature with shivering, confusion or feeling very unwell — seek urgent medical help; do not wait for test results
- A severe or rapidly spreading infection, or one not responding to treatment
- Breathing difficulty, chest pain or a stiff neck with sensitivity to light
- Sudden swelling of the lips, tongue or throat, or difficulty breathing or swallowing
- Unexplained heavy bleeding, severe bruising or a widespread rash
- Feeling faint, breathless or unwell after the blood test itself
Who to contact: your clinician, clinic or test provider first (keep their number to hand). For urgent advice when you can't reach them, call NHS 111. In an emergency, call 999.
General guidance — it doesn't replace the specific advice your specialist gives you.
Results & realistic expectations
A 'normal' set of immune blood tests is reassuring but does not rule out every immune problem, and it does not always explain symptoms such as tiredness or frequent minor colds. Equally, an abnormal or borderline result is not automatically a diagnosis — it is a clue that a specialist must interpret alongside your history and examination.
The most useful results are those that change what happens next: confirming a deficiency that can be treated, ruling out a serious concern, or guiding vaccination and prevention. Results that change nothing, or that simply raise more questions, are a reason to pause and ask your immunologist what they actually mean for you.
Immune test results are a snapshot in time. Antibody levels, complement and autoantibodies can change with infection, pregnancy, medication and age, so a result may need repeating if your situation changes or if it was borderline. A normal result now does not guarantee the same result in future, and a single abnormal result often needs confirming before it is acted on.
Related tests, treatments or support
These tests are often done together as a tailored panel. For example, antibody levels, IgG subclasses and a vaccine-response test may be combined to build a picture of antibody function, while complement and autoantibody tests are added when autoimmune disease is being considered. Your immunologist chooses the combination based on your specific problem rather than testing everything at once.
Follow-up & long-term care
Follow-up depends on the findings. You may be given results by phone, letter or at a clinic appointment. Borderline results are often repeated, vaccine-response testing requires a planned return visit, and clearly abnormal results usually lead to referral to a specialist immunology service. A good service tells you who is responsible for chasing and explaining your results.
- Repeat testing if results were borderline or if your symptoms change
- Keeping vaccinations up to date, as advised by your specialist
- Ongoing monitoring if a deficiency or autoimmune condition is confirmed
- Keeping your own record of results to avoid duplicate tests
Repeat, follow-on and what comes next
- Borderline or mildly abnormal results are common and frequently need repeating before they mean anything.
- Vaccine-response testing is a two-stage process and is incomplete without the second sample.
- A normal result does not exclude every immune problem, and an abnormal one is not automatically a diagnosis.
- Results can change over time with infection, pregnancy, medication and age.
Ask what happens if the result is unclear or needs repeating, and what is included if further tests or follow-up are needed.
What good aftercare looks like
- A named clinician — ideally a consultant immunologist — responsible for interpreting and explaining results.
- A clear process and timeline for receiving results, including borderline ones.
- A plan for repeating tests where needed, and for completing vaccine-response testing.
- Onward referral to a specialist immunology centre if a significant problem is found.
- Honest discussion when results are normal but symptoms continue, including other avenues to explore.
What affects the cost
Costs vary a great deal between people and providers, and we don't publish prices. What matters is understanding what drives the cost and making sure your quote is complete. The main things that affect it:
- How many and which tests are included (a focused panel costs less than broad testing)
- Whether specialist vaccine-response testing, which needs two visits, is required
- The consultant immunologist's fee for interpreting results, not just the lab fee
- Whether a follow-up consultation to explain results is included
- Phlebotomy (blood-taking) and laboratory processing fees
- Any repeat tests needed to confirm borderline results
- The consultant immunologist's fee for ordering and interpreting results
- Each laboratory test fee, itemised, and what is and is not included
- Whether vaccine-response testing (and its second visit) is included
- The cost of a follow-up appointment to discuss results
- What happens, and what it costs, if results are borderline and need repeating
- Who is responsible for explaining abnormal results and arranging next steps
On the NHS? Immune blood tests are available on the NHS when there is a clear clinical reason; private testing is sometimes used for faster access or a second opinion, but results still need expert interpretation.
You're entitled to your total cost in writing — including reports, follow-up and what happens if the result is inconclusive — before you decide.
Consent traps and marketing red flags
These are not small details. They are often where patients lose choice, time to reflect, or realistic expectations.
Consent traps
- Ordering broad panels without explaining what each test is for or what it would change.
- Treating a single abnormal or borderline number as a diagnosis without specialist interpretation.
- Not warning that incidental findings may lead to further, sometimes unnecessary, investigation.
- Not making clear who will interpret results and follow them up.
- Implying that a normal result guarantees a strong immune system or rules out all disease.
Marketing red flags
- 'Complete immune system check' or 'immune MOT' marketed to healthy people with no clear reason.
- Claims that a blood panel can 'boost' or 'optimise' your immune system.
- Selling broad tests directly to consumers without specialist interpretation.
- Promising that tiredness or frequent colds will be explained by an immune test.
- Bundling many autoantibody tests together, increasing the chance of meaningless positives.
Choosing a specialist safely
- Check the specialist is on the GMC Specialist Register for this area.
- Make sure they work at a CQC-registered service, and look for membership of the relevant Royal College or professional body.
- You're entitled to time to consider and to have your questions answered before you agree — the specialist who looks after you should explain it, not a salesperson.
- Be wary of pressure: time-limited offers or deposits taken before you've had time to think are red flags, not bargains.
- You're entitled to your total cost in writing — including any follow-up — before you decide.
Questions to ask your medical professional
Take this to your consultation. A good specialist will welcome every one of these.
- Which specific immune tests are you ordering, and what is each one for?
- What will this result actually change in my care?
- What happens if a result is normal, abnormal or inconclusive?
- Who will interpret abnormal results, and will I see a clinical immunologist?
- Do any of my medicines or recent infections affect these tests?
- If a result is borderline, when should it be repeated?
- Are you on the GMC Specialist Register for this area, and which Royal College or professional body are you a member of?
- Will you be the specialist who carries out my test, and who looks after me afterwards?
- What are the risks for someone like me, and how often do your own patients have a problem or need it repeated or redone?
- What does a realistic result look like — and what can this test not achieve?
- What are my options, including waiting, doing nothing for now, or choosing a different approach?
- Can I have written information, results and aftercare instructions in a format I can use, including any accessibility or communication support I need?
- What is the total cost in writing, including any follow-ups, and how much time do I have to decide?
Frequently asked questions
Can I have these tests on the NHS?
Will one blood test tell me if my immune system is weak?
I keep getting colds — does that mean my immune system is failing?
How long do results take?
What if my result is borderline?
Is a private 'immune screen' or 'wellness panel' worth it?
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How we made this page
Medically reviewed by a GMC-registered consultant. Written in plain English, checked against NHS, NICE, GMC and relevant Royal College / specialist-society guidance, and kept under review. No clinic paid to appear on this page, and we publish no pricing. This is general information to help you prepare — it is not a substitute for advice from your own clinician. How we review our guides →
Source hierarchy: UK regulator and NHS/NICE guidance first, then relevant Royal College or specialist-society guidance, then peer-reviewed evidence for procedure-specific figures where available.
Sources & standards: Lab Tests Online UK — Quantitative Immunoglobulins Immunodeficiency UK — Primary immunodeficiency information British Society for Immunology — Clinical immunology guidelines Newcastle Hospitals NHS — Clinical immunology and allergy referral guidelines BSACI — about clinical immunology and allergy specialists
Reviews reflect patients' experience of care, not clinical outcomes. For procedure volumes and outcome data see PHIN.
Last medically reviewed 2026-09-21. Spotted something wrong or out of date? Report an error in this guide.
Related guides: Immunoglobulin level testing · IgG subclass testing · Vaccine response testing · Complement testing · Autoantibody / autoimmune testing