How long does a cold last vs the flu?

Short answer

A cold lasts 7–10 days and comes on gradually. The flu lasts 1–2 weeks, hits suddenly, and is significantly more severe — high fever, body aches, and exhaustion are the hallmarks. If you feel fine one hour and terrible the next, it's probably flu.

Side-by-side comparison

| Symptom | Cold | Flu | |---------|------|-----| | Onset | Gradual (1–2 days) | Sudden (hours) | | Fever | Rare or mild | Common, 100–104°F | | Body aches | Mild | Severe | | Fatigue | Mild | Severe — can be debilitating | | Headache | Uncommon | Common | | Runny/stuffy nose | Very common | Sometimes | | Sore throat | Common early | Sometimes | | Cough | Mild | Can be severe | | Vomiting/diarrhea | Rare | More common (especially in kids) |

Timeline of each illness

Cold timeline

Day 1–2: Scratchy throat, mild congestion, tiredness
Day 3–4: Peak symptoms — runny nose, sore throat, sneezing
Day 5–7: Symptoms improve, lingering congestion
Day 7–10: Mostly resolved; cough may linger

Flu timeline

Day 1: Sudden onset — fever, chills, severe body aches
Day 2–4: Worst phase — fever peaks, exhaustion, muscle pain
Day 5–7: Fever breaks, starting to improve
Day 7–14: Fatigue and cough can linger for weeks

When to see a doctor

See a doctor for flu if:

Fever above 103°F lasting more than 3 days
Difficulty breathing or chest pain
Confusion or altered mental state
Symptoms improve then suddenly worsen
You're over 65, pregnant, or immunocompromised — antivirals (Tamiflu) work best in the first 48 hours

For a cold, doctor visits are rarely needed unless symptoms last more than 10 days or you develop ear pain, sinus pain, or green discharge lasting more than 10 days.

Common mistakes

Taking antibiotics for either — both are viruses, antibiotics don't help
Returning to work/school too soon — flu is contagious for 5–7 days from symptom onset
Skipping the flu vaccine — it reduces severity even when it doesn't fully prevent infection