Illness & Symptoms
How long does glandular fever last?
Estimated wait
~21 days
Based on published sources
By case
- Faster cases~18 days
- Average cases~21 days
- Slower casesUp to 28 days
The lingering fatigue after the acute illness is normal and does not mean something has gone wrong — but pace yourself, as pushing too hard prolongs it. Avoid contact sport for several weeks: the spleen is often enlarged and can rupture. See a doctor for severe throat swelling, breathing difficulty or sharp pain in the upper left abdomen. General information, not medical advice.
The acute phase of glandular fever (infectious mononucleosis) usually lasts about 2 to 4 weeks — most people are over the main symptoms within roughly three weeks. The fever typically runs for 10 to 14 days, and the tiredness is heaviest in the second and third week.
More details
The exhaustion is the part that outlasts everything else: it can take several more weeks, sometimes months, before you are back to full capacity.
Last updated: 20 Jul 2026
Information is for general knowledge only.