Check your symptoms and see which pattern they fit — a cold, the flu or COVID-19. With an honest note that only a test tells flu and COVID apart, and a separate list of warning signs.
Updated: August 17, 2026 · 🔒 Your data never leaves your browser
A cold usually gives itself away by its onset: it builds gradually, starting with a runny nose and sneezing, while the flu hits within hours with a high fever and body aches. The flu and COVID-19, though, are almost impossible to tell apart by symptoms — they overlap in detail, and only a test settles it. This tool shows which pattern your symptoms fit, but it is not a diagnosis.
Check what you have
Warning signs
More like
Check at least three symptoms to gauge the pattern.
🧪 Why this is not a diagnosis
This is not a diagnosis. The flu and COVID-19 cannot be told apart by symptoms — they overlap almost completely. The only way to distinguish them and guide treatment (such as antivirals in the first days) is a test. Cold symptoms usually need no test; pronounced flu or COVID symptoms are worth testing.
This tool is informational and does not replace a medical exam. It is not designed for children, pregnant people or those with chronic lung or heart disease, who should seek advice sooner for respiratory symptoms.
A cold is most reliably given away by its onset and symptom mix. It builds gradually, starting in the nose and throat, with little fever. The flu is the opposite: an abrupt start, high fever, aches and exhaustion, with a runny nose in the background.
The flu and COVID-19, though, cannot be separated by symptoms. Both cause fever, cough, weakness, headache and aches. The one semi-specific difference is loss of smell in COVID, and even that is unreliable. So the tool honestly flags when your checked symptoms fit all three equally.
Check what you have
Warning signs
More like
Check at least three symptoms to gauge the pattern.
🧪 Why this is not a diagnosis
This is not a diagnosis. The flu and COVID-19 cannot be told apart by symptoms — they overlap almost completely. The only way to distinguish them and guide treatment (such as antivirals in the first days) is a test. Cold symptoms usually need no test; pronounced flu or COVID symptoms are worth testing.
This tool is informational and does not replace a medical exam. It is not designed for children, pregnant people or those with chronic lung or heart disease, who should seek advice sooner for respiratory symptoms.
Some signs matter more than any "symptom diagnosis". Trouble breathing, chest pain, confusion and bluish lips are reasons to seek care immediately, whether it is a cold, the flu or COVID.
| Sign | Cold | Flu | COVID-19 |
|---|---|---|---|
| Onset | Gradual | Abrupt | Gradual |
| Fever | Rare, mild | Often high | Common |
| Body aches | Mild | Marked | Moderate |
| Runny nose, sneezing | Common | Sometimes | Sometimes |
| Loss of smell | Sometimes | Rare | Characteristic |
| Shortness of breath | No | Rare | Possible — a warning sign |
Читайте также: Frequent colds in adults: when it is normal and when it is not
Most "immune boosters" and megadoses of vitamin C do not prevent colds or shorten them to any meaningful degree. What actually works is sleep, movement, diet, and vaccination against flu and COVID for those for whom it is indicated.
Читайте также: How to boost immunity: what works and what is marketing
Читайте также: Vitamin C and colds: what the research shows
The tool is designed for adults without serious chronic illness. Children, pregnant people and those with lung or heart disease should see a doctor sooner for respiratory symptoms rather than rely on self-assessment: for them an ordinary cold more often leads to complications.
By speed and severity. A cold develops gradually over 1–2 days; the main symptoms are a runny nose, sneezing and sore throat, with little or no fever. The flu starts abruptly: a high fever, body aches, marked weakness and headache appear within hours, while a runny nose is less prominent.
Not reliably. Fever, cough, weakness, aches and headache occur in both. Loss of smell is slightly more characteristic of COVID, but it also happens with nasal congestion and not with every variant. The only way to tell them apart and start antivirals in time is a test.
With pronounced flu or COVID symptoms — high fever, marked weakness, cough — a test is worth it: it guides management, including antivirals that only work in the first days. Mild cold symptoms usually need no test. People in contact with vulnerable individuals are a separate case for testing.
Trouble breathing or breathlessness at rest, chest pain or pressure, confusion, and bluish lips or face are reasons to seek help immediately — for breathing problems, call emergency services. A 'second worsening' — feeling better, then suddenly worse — is also a warning sign.
A cold usually clears in 7–10 days, though a cough can linger. The flu has an acute phase of 3–5 days with weakness lasting longer. COVID-19 is more variable: from a few days to a couple of weeks, and in some people certain symptoms drag on. In all cases, prolonged or worsening illness is a reason to see a doctor.
No. It is an informational tool that helps you orient yourself, not a diagnosis. Children, pregnant people and those with chronic lung or heart disease should seek advice sooner for respiratory symptoms rather than rely on self-assessment.
How many colds a year is normal, why a weak immune system is rarely the answer, which warning signs need investigation, and what genuinely reduces how often you get ill.
You can't 'boost' immunity with a pill. Here's what actually helps — sleep, movement, food, vaccines — and why immune boosters and vitamin megadoses do nothing.
Vitamin C doesn't prevent colds in most people, but cuts their length by about 8%. We unpack the myths, doses, the absorption ceiling, and zinc.