Mono: What It Is and How to Get Through It
Last updated September 10, 2026.
Mononucleosis (mono) is a viral infection that causes extreme fatigue, severe sore throat, swollen lymph nodes, and sometimes an enlarged spleen. Most people recover in 2 to 4 weeks with rest, though tiredness can persist for months. The main risks are rupturing an enlarged spleen during contact sports and mistaking mono for strep throat.
What mono feels like
Mono starts with fatigue that feels disproportionate to a typical cold. You may sleep 12 hours and still feel exhausted. The sore throat is usually severe, often mistaken for strep, with white patches on the tonsils and swollen glands in the neck.
Fever runs between 100°F and 104°F for the first week or two. Some people develop a rash, especially if they take amoxicillin (prescribed mistakenly for strep). Loss of appetite and mild abdominal discomfort on the left side are common when the spleen enlarges.
Symptoms peak in the first two weeks, then gradually improve. Fatigue is the last symptom to resolve and can linger for 6 to 8 weeks or longer in some cases.
Testing and diagnosis
A rapid strep test usually comes first because strep and mono look similar. If the strep test is negative but your throat is very sore with fatigue, your provider may order a monospot test or Epstein-Barr virus (EBV) antibody test. The monospot can give false negatives in the first week, so timing matters.
Blood work may show elevated liver enzymes and atypical lymphocytes, white blood cells that appear in viral infections. Not everyone needs testing. If symptoms are classic and mild, some providers skip tests and manage based on the clinical picture.
Mono is caused by the Epstein-Barr virus in about 90% of cases. Other viruses, including cytomegalovirus, can cause similar illness. Testing distinguishes mono from strep because strep needs antibiotics and mono does not.
The spleen rule for sports and physical activity
About half of people with mono develop an enlarged spleen (splenomegaly) during the illness. The spleen sits under the left ribcage and filters blood. When enlarged, it becomes fragile and can rupture from a blow to the abdomen, causing internal bleeding that requires emergency surgery.
Avoid contact sports, heavy lifting, and any activity with risk of abdominal impact for at least 3 to 4 weeks from symptom onset. Some providers recommend waiting until you feel fully recovered or getting an ultrasound to confirm the spleen has returned to normal size before resuming contact sports.
Light activity like walking is fine once fever resolves. Listen to your body. Pushing through fatigue does not speed recovery and can make exhaustion worse.
Treatment and recovery timeline
There is no antiviral treatment for mono. Care focuses on rest, fluids, and symptom relief. Over-the-counter pain relievers like acetaminophen or ibuprofen help with fever and sore throat. Avoid aspirin in children and teens due to the risk of Reye's syndrome.
Most people feel significantly better within 2 to 4 weeks. Severe fatigue can persist for 2 to 3 months in some cases. Returning to school or work part-time and gradually increasing activity helps more than strict bed rest after the first week or two.
Mono is not usually contagious after symptoms resolve, but the virus can shed in saliva intermittently for months. Avoid sharing drinks, utensils, or kissing new partners until you are fully recovered. By adulthood, most people have been exposed to EBV and have immunity.
When to see a provider or go to the ER
See a provider if you have severe sore throat with fatigue lasting more than a few days, especially if you also have fever and swollen glands. Strep needs to be ruled out, and mono diagnosis helps set expectations for recovery time and activity restrictions.
Go to the ER or call 911 if you have sudden, sharp abdominal pain (especially on the left side), lightheadedness, or fainting. These can signal a ruptured spleen. Also seek emergency care if you have difficulty breathing, severe headache with stiff neck, or signs of dehydration.
Urgent care can run a strep test and monospot if you need a diagnosis outside regular office hours. Costs typically run $150 to $250 without insurance. Some community health centers offer sliding-scale fees.
Getting care and cost considerations
A primary care visit for mono evaluation costs $150 to $300 without insurance. Testing (monospot and complete blood count) adds $50 to $150. If you have insurance, a copay usually applies. Federally qualified health centers charge based on income and accept uninsured patients.
Telehealth works well for initial evaluation if symptoms are classic and you need guidance on rest, activity restrictions, and when to escalate care. Some platforms charge $40 to $80 per visit. A free AI doctor consult by text can help determine whether in-person evaluation is necessary.
Most mono cases do not require prescription medication. Rare severe cases with airway swelling from enlarged tonsils may need corticosteroids, which cost $10 to $30 for a short course.
Common questions
How long does mono last?
Most people feel significantly better within 2 to 4 weeks, but fatigue can persist for 2 to 3 months. Fever and sore throat usually resolve in the first 10 to 14 days. The timeline varies, and pushing through exhaustion can prolong recovery.
Can you get mono more than once?
True mono from Epstein-Barr virus usually happens only once because you develop lifelong immunity. Rarely, other viruses cause mono-like illness, which can happen more than once. Reactivation of EBV in people with weakened immune systems is possible but uncommon.
When can I go back to sports after mono?
Wait at least 3 to 4 weeks from symptom onset before returning to contact sports or activities with risk of abdominal impact. Some providers recommend waiting until you feel fully recovered or confirming spleen size with ultrasound. Light activity like walking is safe once fever resolves.
Is mono contagious after symptoms go away?
You can shed the virus in saliva intermittently for months after recovery, but the risk of transmission drops significantly once symptoms resolve. Avoid sharing drinks or close contact with new partners until fully recovered. Most adults already have immunity from prior exposure.
Do I need antibiotics for mono?
No, mono is caused by a virus and does not respond to antibiotics. Antibiotics are needed only if you also have a bacterial infection like strep throat, which requires a separate positive test. Taking amoxicillin with mono often causes a rash.
What does an enlarged spleen feel like with mono?
Many people do not feel an enlarged spleen at all. Some notice mild discomfort or fullness under the left ribcage. Sudden, sharp pain on the left side, especially with lightheadedness, is a medical emergency and may signal a rupture.
Sources
- CDC - Epstein-Barr Virus and Infectious Mononucleosis
- MedlinePlus - Mononucleosis
- HRSA - Find a Health Center
Pymander is not a replacement for a physician and does not provide medical advice, diagnosis, or treatment.