Answers to the Common Questions on Colds and Flu
Colds and Flu: straight answers to the questions people actually ask, with the figures behind them.
Two different viral illnesses that share a season and very little else.
Key takeaways
- Cold onset: gradual, over 1-2 days
- Flu onset: abrupt, over hours
- Most useful single change: Have the annual flu vaccine if you are eligible.
- Commonest mistake: Asking for antibiotics, which do not work on viruses.
- See a doctor if any of the signs under "When to speak to a doctor" below apply to you.
What is Colds and Flu?
Two different viral illnesses that share a season and very little else.
Why does it matter?
Onset speed separates them in practice, and it matters because one of them has a vaccine and antivirals.
Cold onset for Colds and Flu?
Gradual, over 1-2 days.
Flu onset for Colds and Flu?
Abrupt, over hours.
Typical cold duration for Colds and Flu?
About 7-10 days.
Antiviral window for flu for Colds and Flu?
Usually within 48 hours of onset.
What is the single most useful thing to do?
Have the annual flu vaccine if you are eligible.
What is the most common mistake?
Asking for antibiotics, which do not work on viruses.
When should I see a doctor?
Contact a GP or NHS 111 if you are over 65, pregnant, immunosuppressed, or have a long-term condition and develop flu symptoms. Call 999 for difficulty breathing, chest pain, coughing up blood, confusion, a rash that does not fade under pressure, or a child who is struggling to breathe, floppy or will not wake.
Where to go next
- Colds and Flu in Five Minutes
- Colds and Flu: What Published Guidance Supports
- Colds and Flu — the reference entry
- The Evidence on Antibiotics, Without the Hype
- What the Guidance Really Says About Hand Hygiene
When to speak to a doctor
Contact a GP or NHS 111 if you are over 65, pregnant, immunosuppressed, or have a long-term condition and develop flu symptoms. Call 999 for difficulty breathing, chest pain, coughing up blood, confusion, a rash that does not fade under pressure, or a child who is struggling to breathe, floppy or will not wake.
Where this comes from
How this page was put together
Every figure, recommendation and warning above is taken from the guidance named in Where this comes from. Nothing on this page is inferred, summarised or generalised beyond what those bodies publish: where they give a number, it is their number, and where they are silent, so are we. Pages are rebuilt whenever the underlying record changes. Sign-off by a named clinician, where it has happened, is shown at the top of the page along with the date.
Medical disclaimer
This article is general information, not medical advice. It cannot account for your own history, medication or circumstances. Always speak to a GP, pharmacist or another qualified health professional before making changes that affect your treatment, and never delay seeking medical advice because of something you have read here. In an emergency, call 999.
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