Flu symptoms vs a cold: how to tell and what to do

In short

• Flu usually comes on suddenly; a cold comes on gradually.
• Fever, body aches, headache and heavy fatigue point toward flu rather than a cold.
• Sneezing, a stuffy or runny nose and a sore throat are the main features of a cold.
• Antibiotics do not work on viruses, so they do not shorten a cold or the flu.
• A yearly flu shot is the most important step to lower your risk of a hard flu season.

How flu differs from a cold

Colds are caused by a range of respiratory viruses, and flu is caused by influenza viruses. In practice you tell them apart by how fast they start and how heavy you feel. A cold tends to stay in the nose and throat and usually leaves you well enough to carry on. Flu affects the whole body and often leaves you too worn out for normal activities.

1. StartFlu usually comes on suddenly, while a cold develops over two or three days, often beginning with a scratchy throat.
2. FeverFever is common with flu and often lasts three to four days. It is rare with a cold. Not everyone with flu has a fever, though.
3. Aches and headacheBody aches and headache are common with flu and can be severe. With a cold they are slight or absent.
4. Nose and throatSneezing and a stuffy nose are common with a cold and only sometimes seen with flu.
5. TirednessFatigue is usual with flu and only occasional with a cold.

One caveat matters. You cannot reliably tell flu from COVID-19 by symptoms alone, and other viruses cause a similar picture. If the answer changes what you do, for example because you are at higher risk, a test is the only way to know.

What the illness usually looks like

After exposure, flu symptoms typically appear within one to four days. Most people recover within about a week, although a cough and tiredness can linger for two weeks or more. A cold usually gets better within one to two weeks.

• Early days: with flu, the worst of the fever, aches and headache; with a cold, a blocked nose and sore throat.
• Middle days: fever usually fades, and a cough may start or get worse.
• Later: the main symptoms ease, though a dry cough and low energy are common afterwards.
• If you start to feel better and then the fever or cough returns or gets worse, that is a reason to be seen.

What helps at home

For both illnesses, home care means easing symptoms while your body clears the virus. These measures are reasonable for most healthy adults.

• Rest and sleep, rather than pushing through the day.
• Plenty of fluids, such as water, broth or weak tea.
• Saline nasal spray or rinse to ease a blocked nose.
• A clean humidifier or a steamy bathroom to soothe airways.
• Throat lozenges or gargling with salt water for a sore throat.
• Honey for a cough in anyone at least one year old; never give honey to babies under 12 months.
• Over-the-counter pain relievers and fever reducers for comfort, after checking with a pharmacist or your provider.

Be careful with combination cold products. Many contain the same active ingredient as a separate pain reliever, so using two together can mean taking too much without noticing. Ask a pharmacist, especially if you take medicine for blood pressure, diabetes or liver disease. Over-the-counter cough and cold medicines are not recommended for children under 6, and aspirin should not be given to children or teenagers with a viral illness.

Antibiotics and antiviral medicine

Antibiotics do not work on viruses and will not help you feel better. Taking them when you do not need them can still cause side effects. The color of nasal mucus does not decide the question, and your provider looks at the whole picture and how long you have been ill.

Flu is different in one respect. Prescription antiviral drugs can make flu milder and shorten it by about a day, and they work best when started within two days of the first symptoms. They are recommended for people at higher risk of complications, such as those with asthma, diabetes or heart disease, and most people who are not at higher risk do not need them. They are not sold over the counter, so the decision belongs to a clinician.

Lowering your risk

• Get a flu vaccine every season. CDC advises everyone 6 months and older to get one, ideally by the end of October.
• Wash your hands often with soap and water, or use an alcohol-based hand rub, and avoid touching your eyes, nose and mouth.
• Cover coughs and sneezes and throw tissues away promptly.
• Keep your distance from people who are sick, and stay home when you are sick.
• Bring in fresh air or gather outdoors when you can.

A mask worn by a sick person reduces spread to others and can also protect the wearer. Supplements are heavily marketed, but there is little evidence that vitamin C, echinacea or garlic help with colds, and the flu shot does not prevent colds.

When you can go back to normal life

CDC advises staying home until your symptoms are improving overall and you have been without a fever for at least 24 hours without using a fever reducer. After that, extra precautions such as cleaning frequently touched surfaces and improving indoor air help protect others. Adults with flu are most contagious in the first three days of illness, and young children and people with weakened immune systems can spread it for longer. If you live with someone at higher risk, extra distance in the first days makes sense.

Red flags and when to see a doctor

Red flags: call 911 or go to an emergency department for difficulty breathing or shortness of breath, persistent pain or pressure in the chest or abdomen, persistent dizziness or confusion, inability to stay awake, seizures, not urinating, severe muscle pain or weakness, or fever or cough that improves and then returns or gets worse. In children, also watch for fast or hard breathing, bluish lips or face, ribs pulling in with each breath, signs of dehydration, being hard to wake or not interacting, and any fever in a baby under 12 weeks.

Book an appointment with your primary care provider if a fever lasts more than three to four days, symptoms have not improved after 10 days, ear or sinus pain gets worse, or a cough lasts more than three weeks. Contact your provider early if you are pregnant, 65 or older, or have a chronic lung, heart, kidney or liver condition, diabetes or a weakened immune system, because early treatment can change the plan.

Questions to ask your provider

• Do I need a flu or COVID-19 test, given my symptoms and risk factors?
• Should I be considered for antiviral treatment?
• Which over-the-counter products are safe with my regular medicines?
• How might this infection affect my long-term condition?
• Which vaccines are recommended for me this season?

Questions and answers

Sources

1. CDC — Signs and Symptoms of Flu
2. CDC — Treatment of Flu
3. CDC — Preventing Flu
4. CDC — Flu Vaccine Safety
5. CDC — Colds: when antibiotics do not help
6. NHS — Common cold

Sources checked on 29 October 2026.