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Health condition · Clinically reviewed

Glandular fever, the sore throat that isn't bacterial - and why the treatment is time.

Fever, a severe sore throat and swollen glands that won't budge - infectious mononucleosis is common, usually self-limiting, and has one important prescribing trap to avoid.

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Why trust this guide

  • 01

    Clinically reviewed

    Written by our editorial team and reviewed by a registered UK clinician before publication.

  • 02

    Sourced from guidance

    Checked against NICE CKS and peer-reviewed sources you can see at the end.

  • 03

    Current for 2026

    Reflects modern UK guidance on diagnosis, the amoxicillin rash pitfall, and splenic rupture safety-netting.

Key facts

Glandular fever at a glance.

The essentials, in plain English - what it is, how it spreads, and the one prescribing pitfall everyone should know.

  • What it is

    An acute viral illness, most often caused by the Epstein-Barr virus (EBV), producing fever, sore throat and swollen glands.

  • Also known as

    Glandular fever, "mono", or "the kissing disease" - EBV spreads readily via saliva.

  • Who gets it

    Most common in teenagers and young adults - often mild or silent in young children.

  • Classic triad

    Fever, sore throat with pharyngeal exudate, and prominent lymphadenopathy - especially posterior cervical nodes.

  • Key precaution

    Avoid amoxicillin or ampicillin if mononucleosis is suspected - both can trigger a widespread rash.

  • Main risk

    Splenomegaly means contact sports and heavy lifting must be avoided for several weeks, given the risk of splenic rupture.

Why this guide matters

Recognise it, protect the spleen, ride it out.

Glandular fever is common, self-limiting in most people, and comes with two things worth understanding early. The points below shape everything else on this page.

  • The triad points the way

    Fever, severe sore throat and prominent lymphadenopathy - especially posterior cervical nodes - point strongly to glandular fever over ordinary tonsillitis.

  • Amoxicillin is the trap to avoid

    Giving amoxicillin or ampicillin for what looks like bacterial tonsillitis can trigger a dramatic, widespread rash if the real cause is EBV.

  • The spleen needs time

    Splenomegaly means avoiding contact sports and heavy lifting for weeks - the single most important safety measure during recovery.

How the diagnosis is made

From a sore throat to a confirmed cause.

The steps a UK GP will normally follow, in order - so you know what to expect and why amoxicillin gets avoided along the way.

  1. 01

    Assessing

    Clinical assessment

    The characteristic triad of fever, severe sore throat and lymphadenopathy, alongside examination for splenomegaly and hepatomegaly.

  2. 02

    Assessing

    Full blood count and film

    Looks for lymphocytosis with atypical lymphocytes on blood film - a strong supporting feature.

  3. 03

    Assessing

    Throat swab if uncertain

    Used to exclude or identify concurrent bacterial infection, particularly group A streptococcus, when the picture is unclear.

  4. 04

    Confirming

    Monospot (heterophile antibody)

    A rapid screening test - though it can be falsely negative early in the illness or in young children.

  5. 05

    Confirming

    EBV-specific serology

    EBV VCA IgM and IgG, plus EBNA, give a more definitive answer, particularly if the Monospot is negative but suspicion remains.

  6. 06

    Confirming

    Liver function tests

    Often mildly deranged given the hepatic involvement that frequently accompanies the illness.

  7. 07

    Prescribing safely

    Avoid amoxicillin/ampicillin

    A key prescribing safeguard - giving these antibiotics for presumed bacterial tonsillitis risks triggering the classic EBV rash.

Typical timeline: a first assessment to a confirmed diagnosis within days.

Symptoms

What glandular fever actually feels like.

The classic triad plus the features that distinguish it from an ordinary throat infection - and the one sign that needs emergency care.

  • Fever

    Often sustained for a week or more, part of the classic triad alongside sore throat and lymphadenopathy.

  • Severe sore throat

    Frequently with visible pharyngeal exudate, closely mimicking bacterial tonsillitis - see our tonsillitis guide.

  • Lymphadenopathy

    Prominent, often marked posterior cervical node swelling - a distinguishing feature from ordinary bacterial pharyngitis.

  • Profound fatigue

    Can be severe and prolonged, sometimes persisting for weeks to months after other symptoms settle.

  • Splenomegaly

    An enlarged spleen is common and carries a real risk of rupture with contact sports or abdominal trauma during the illness.

  • Hepatomegaly and mild hepatitis

    Some patients develop liver enlargement or mildly deranged liver function alongside the acute illness.

  • Rash after amoxicillin

    A widespread maculopapular rash - a classic clinical pearl - if amoxicillin or ampicillin is given for presumed bacterial tonsillitis.

  • Red flag - severe abdominal pain

    Sudden severe left-sided abdominal pain can signal splenic rupture - a medical emergency needing immediate attention.

Treatment

How glandular fever is managed in the UK.

Supportive care and time do the heavy lifting - with clear precautions around the spleen, and hospital care reserved for genuine complications.

  • Supportive care

    The mainstay of treatment - rest, adequate fluids, and simple analgesia or antipyretics such as paracetamol or ibuprofen for fever and throat discomfort.

  • Avoid contact sports and lifting

    For at least three to four weeks, sometimes longer, guided by resolution of splenomegaly - protecting against splenic rupture.

  • Graded return to activity

    Given how profound and prolonged fatigue can be, a gradual return to school, work or exercise as tolerated, rather than a fixed timeline.

  • Corticosteroids in severe cases

    A short course considered for significant airway compromise from tonsillar swelling or severe haematological complications - specialist guidance.

  • Hospital admission

    For airway obstruction, severe dehydration, or suspected splenic rupture with severe abdominal pain - an emergency requiring urgent assessment.

  • Monitoring for complications

    Though rare, includes splenic rupture, upper airway obstruction, haemolytic anaemia and, rarely, chronic active EBV infection.

  • No specific antiviral treatment

    No antiviral is routinely recommended for uncomplicated glandular fever - supportive measures remain the standard approach.

  • Avoiding amoxicillin/ampicillin

    An important prescribing consideration - these antibiotics should not be given if infectious mononucleosis is suspected, to avoid the characteristic rash.

What this guide is based on

The sources behind every claim on this page.

UK national guidance and specialist society standards, current at the time of last review.

Key references

Guidelines and standards we relied on.

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, get seen.

  • NICE CKS. Glandular fever (infectious mononucleosis).

  • Public Health England / UKHSA. Guidance on EBV and glandular fever.

  • British Society for Haematology. Guidance on atypical lymphocytosis and blood film interpretation.

  • Royal College of Emergency Medicine. Guidance on splenic injury and safety-netting.

Red flags

When glandular fever needs urgent attention.

Most cases are managed at home with rest and simple analgesia. These are the situations that aren't - and where urgent care is needed.

  • Suspected splenic rupture

    Sudden, severe abdominal pain, particularly left-sided or radiating to the shoulder, is a medical emergency - call 999 or attend A&E immediately.

  • Upper airway obstruction

    Severe tonsillar swelling causing breathing difficulty or stridor needs urgent hospital assessment and may require corticosteroids.

  • Severe dehydration

    Inability to maintain oral fluid intake because of throat pain warrants hospital admission for supportive care.

  • Persistent high fever beyond two weeks

    Should prompt review to reconsider the diagnosis or check for a secondary bacterial infection.

  • Jaundice or marked abdominal pain

    May reflect significant hepatic involvement and needs clinical review with liver function testing.

  • Rash after amoxicillin or ampicillin

    A widespread rash following these antibiotics strongly suggests glandular fever rather than a drug allergy - review the diagnosis.

  • Haemolytic anaemia

    Rare but recognised - unusual pallor, jaundice or breathlessness should prompt a full blood count and clinical assessment.

  • Neurological symptoms

    Severe headache, neck stiffness, confusion or seizures need urgent assessment to exclude encephalitis - see our encephalitis guide.

  • Symptoms in immunocompromised patients

    EBV infection can behave differently and more severely in those who are immunosuppressed - specialist input is needed early.

Living with it

A self-limiting illness, with a few firm rules.

Four things that make the biggest difference during recovery - pacing yourself, protecting the spleen, simple comfort measures, and knowing the emergency signs.

A quiet reminder

Most people recover fully - it just takes longer than a cold.

Fatigue can outlast the fever and sore throat by weeks. That is normal, not a sign something else is wrong.

  1. 01 Rest

    Pace yourself

    Fatigue can linger for weeks or months after the fever and sore throat settle - build in rest rather than pushing through.

  2. 02 Safety

    Protect your spleen

    No contact sports, heavy lifting or vigorous exercise for at least three to four weeks, or until your clinician confirms the spleen has settled.

  3. 03 Comfort

    Simple measures help most

    Paracetamol or ibuprofen, warm fluids and rest do more for comfort than any specific medicine - there is no antiviral cure needed here.

  4. 04 Escalate

    Know the emergency signs

    Sudden severe abdominal pain or breathing difficulty means urgent medical attention - don’t wait it out.

Frequently asked

Everything we get asked about glandular fever.

Quick answers on how it spreads, testing, the amoxicillin rash, and how long recovery takes.

  • What is infectious mononucleosis?

    A viral illness, most commonly caused by the Epstein-Barr virus, producing the classic triad of fever, severe sore throat and prominent lymphadenopathy. It is also known as glandular fever, "mono", or "the kissing disease" because EBV spreads readily through saliva.

  • How is glandular fever actually caught?

    Primarily through saliva - hence the "kissing disease" nickname - though other close contact can also spread it. Most people are exposed to EBV at some point in life, but symptomatic illness is most common in teenagers and young adults.

  • Why can’t I be given amoxicillin for my sore throat?

    If infectious mononucleosis is even suspected, amoxicillin and ampicillin should be avoided. Giving either drug when the underlying cause is EBV rather than bacterial tonsillitis very often triggers a widespread, itchy maculopapular rash - a classic and well-recognised clinical pearl.

  • Why do I need to avoid sport and heavy lifting?

    Glandular fever commonly causes splenomegaly, an enlarged spleen that is more vulnerable to rupture with contact sports, heavy lifting or abdominal trauma. Avoiding these activities for at least three to four weeks, sometimes longer, is an important safety measure, particularly for young athletic patients.

  • How is the diagnosis confirmed?

    Diagnosis is largely clinical, based on the classic triad and examination findings, supported by a full blood count showing lymphocytosis with atypical lymphocytes. A Monospot (heterophile antibody) test gives rapid confirmation, though it can be falsely negative early on or in young children, in which case EBV-specific serology is used.

  • How long does the fatigue last?

    This is one of the more frustrating features of the illness - fatigue can be profound and, in some people, persists for weeks to months after the fever and sore throat have resolved. A graded return to normal activity, rather than a fixed timeline, is the usual advice.

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