Health condition
IgG subclass deficiency
IgG subclass deficiency - low levels of one or more of IgG1-4 despite a normal total IgG - is a controversial label: it only matters when paired with genuine infections and demonstrably poor vaccine responses, which is what testing should establish.
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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Total IgG can be normal while a subclass (commonly IgG2 in adults with infections) runs low - and many people with low subclasses are perfectly healthy
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The meaningful combination: recurrent bacterial respiratory infections PLUS low subclass PLUS failure to respond to test vaccination
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IgG2 relates to responses against polysaccharide-coated bacteria (pneumococcus, haemophilus) - the organisms behind most sinus and chest infections
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Management is stepped: vaccination (including conjugate vaccines), prompt or prophylactic antibiotics, and immunoglobulin replacement only for proven, significant cases
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Isolated low subclasses without infections generally need no treatment - avoid both under- and over-diagnosis
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
The four IgG subclasses divide the antibody workload: IgG1 and IgG3 handle proteins and viruses, IgG2 specialises in the sugar capsules of bacteria like pneumococcus. A person can carry a respectable total IgG yet lack the specialist - and suffer exactly the infections that specialist prevents: recurrent sinusitis, bronchitis, pneumonia. Equally, population studies find low subclasses in plenty of people who never get ill, which is why the number alone diagnoses nothing and function testing is the heart of the assessment.
Diagnosis and treatment routes
An immunologist frames it functionally: document the infection burden, measure subclasses and baseline pneumococcal antibodies, vaccinate and re-measure at four to six weeks. A failed response in an infection-prone patient justifies action - conjugate vaccination strategies, winter antibiotic prophylaxis, and immunoglobulin replacement for the minority with continuing significant infections; a brisk response reassures and redirects the search. If recurrent respiratory infections keep returning and no one has tested beyond a full blood count, ask for immunology referral - private appointments are typically available within about two weeks.
Seeing a specialist
Who to see, and how quickly you can be seen.
The specialist for this condition is usually a consultant clinical 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 IgG subclass deficiency.
Quick, plain-English answers to what people ask us most.
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Can you explain what IgG subclass deficiency is?
IgG subclass deficiency 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 igG subclass deficiency happen?
There are usually several contributing factors behind igG subclass deficiency, 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 igG subclass deficiency?
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 igG subclass deficiency?
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 igG subclass deficiency 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 igG subclass deficiency 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 igG subclass deficiency 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 igG subclass deficiency?
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 igG subclass deficiency?
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 is it worth getting igG subclass deficiency checked by a specialist?
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.