How long does flu last? A day-by-day recovery guide
Flu hits fast and usually lifts within a week, but the cough and tiredness can hang on. This guide walks through each stage, how long you are infectious over the Christmas visits, who should get the flu vaccine and when to get help.
Flu usually lasts 3 to 7 days, with the worst of it in the first 2 to 3 days. Symptoms start 1 to 4 days after you catch it, often suddenly, with a high temperature, aches and exhaustion. Most people feel much better within a week, but tiredness can last up to 2 weeks and a cough 3 weeks or more. How long flu lasts for you depends on your age, your health and any complications. If you are not improving after 7 days, or you are in a higher-risk group, our doctor can assess you by video.
Timeline
How long does flu last? The day-by-day timeline
Flu (influenza) follows a fairly predictable course in healthy adults. The timeline below is a guide; children, older adults and people with long-term conditions are often ill for longer.
| When | What usually happens |
|---|---|
| Before symptoms (1 to 4 days, often 2) | The incubation period. You feel well, but the virus is already multiplying and you may pass it on. |
| Days 1 to 3 | Symptoms arrive within hours: high temperature, aches, chills, exhaustion, headache and a dry cough. Whole-body symptoms such as fever and aches tend to peak around day 2, and overall symptoms around day 3. |
| Days 4 to 7 | The temperature settles and aches ease. Most people feel clearly better by the end of the first week. |
| Week 2 | Tiredness and low energy are common. You can return to normal activities gradually. |
| Weeks 2 to 3 and beyond | A dry cough can linger for 3 weeks or more, especially in children, older adults and people with lung conditions. |
In volunteer studies of healthy adults, the amount of virus people shed rose sharply within a day of infection, peaked on day 2 and lasted about 5 days on average. That is why the first few days matter most for keeping flu away from others.
Sources: ECDC factsheet on seasonal influenza; Carrat et al., 2008; national patient guidance on flu (see Sources).
Symptoms
Flu symptoms: how flu usually starts
The hallmark of flu is speed. Many people can name the hour they started to feel ill.
Common flu symptoms include:
- A sudden high temperature of 38 degrees or above
- Aches and pains and chills
- Feeling tired or exhausted, too unwell to carry on as normal
- A dry cough, sore throat and headache
- Difficulty sleeping and loss of appetite
- Diarrhoea, tummy pain, nausea or vomiting, which are more common in children
Children have similar symptoms but may also have ear pain and seem less active than usual. Flu and COVID-19 can be hard to tell apart without a test, and both can make children, older adults and people with underlying health problems very unwell.
Recovery
Why the cough and tiredness can last for weeks
Feeling better is not the same as feeling fully recovered. The fever goes first; energy and a settled chest come later.
After the infection clears, the airways can stay irritated for some time, so a dry cough often continues after everything else has improved. Tiredness of up to 2 weeks is common. People with a weakened immune system can be ill for longer overall.
A lingering cough on its own, with no fever and steady improvement, is usually part of normal recovery. What matters is the direction of travel. Symptoms that improve and then get worse again, a temperature that comes back, or new breathlessness are not part of the normal course and should be checked by a doctor.
Is it a chest infection?
Many people describe a cough that hangs on after flu as a "chest infection". A chest infection is an infection of the lungs or large airways. It can be caused by a virus, such as flu, or by bacteria. Most are viral: symptoms usually improve within 7 to 10 days, although the cough and mucus can last up to 3 weeks. Antibiotics do not work on viral infections, including flu, so they only help when the infection is bacterial.
Our doctor can check whether your cough fits normal recovery or points to a bacterial chest infection. Speak to a doctor if you feel very unwell or your symptoms get worse, you cough up blood or blood-stained mucus, or your cough lasts more than 3 weeks.
Source: Chest infection (Ireland’s public health service).
Christmas visits
How long you are infectious, and what it means for Christmas
You can pass flu on shortly before symptoms start, but you shed the most virus in the first few days of the illness.
Young children, older people and people with weakened immune systems tend to shed the virus for longer than healthy adults. In Ireland, the advice is to stay at home while unwell and avoid contact with other people until 48 hours after your symptoms improve. You do not need to stay at home if only a cough or tiredness remains.
December brings crowded homes, long journeys and visits to older relatives. If you or your children have flu symptoms:
- Postpone visits to vulnerable relatives or friends, nursing homes and hospitals until 48 hours after symptoms improve.
- Cover coughs and sneezes with a tissue, bin it straight away, or use your upper sleeve.
- Wash your hands with soap and water, or use an alcohol-based hand rub.
- Consider a mask in busy indoor places such as public transport, crowded shops and places of worship, especially if they are poorly ventilated.
- If you need medicines, ask someone else to collect them so you are not out while unwell.
Sources: ECDC factsheet on seasonal influenza; Carrat et al., 2008; national patient guidance on flu (see Sources).
Self-care
Looking after yourself at home
For most healthy adults, flu is treated at home. Treatment eases symptoms while your immune system clears the virus.
- Rest. Your body needs it, and staying at home protects others.
- Drink enough fluids to avoid feeling thirsty. Fever and a poor appetite make dehydration more likely.
- Paracetamol can ease a high temperature and aches. Follow the dose on the pack and do not combine products that contain the same medicine.
- Eat when you feel ready. A poor appetite for a few days is normal.
- Keep an eye on others in the house, especially babies, older relatives and anyone with a long-term condition.
A high temperature is a sign that your body is fighting the infection and it usually settles by itself. Use medicine to stay comfortable, not to hide a fever that keeps rising or returning.
Medicines
Do antivirals or antibiotics shorten flu?
Antibiotics do not work against flu. It is a virus, so antibiotics will not relieve the symptoms or speed up recovery.
Antiviral medicines for flu, such as oseltamivir, do exist. National guidance for Ireland, updated in September 2026, says antivirals are not recommended for non-severe flu, even for people in higher-risk groups. For most people, the right treatment is rest, fluids and symptom relief such as paracetamol.
Antivirals are reserved for severe or worsening illness, which is usually managed in hospital. They work best when started within about 48 hours of symptoms starting. In some situations, such as a very high-risk person who has been in close contact with someone with flu, a doctor may consider preventive antiviral treatment. Whether that applies to you is a clinical decision made after an assessment.
Source: HPSC, antiviral treatment and prophylaxis guidance (version 4.1, September 2026); ECDC factsheet.
Safety
When flu is more than a rough week
Flu can lead to complications. The most common is pneumonia; bronchitis and ear infections also occur. Flu can also make asthma, COPD and heart failure worse.
You are more likely to develop complications if you are aged 65 or over, are pregnant, have a long-term medical condition, or are a child or teenager aged 2 to 17. Speak to a doctor promptly if:
- You or someone in your household is in a higher-risk group and has flu symptoms.
- Symptoms are not improving as expected, or have not improved after 7 days.
- You feel something is "not quite right", or you are worried about your baby or child.
Prevention
Flu vaccine: who should get it, and timing before Christmas
Irish national guidance calls the flu vaccine the best way to protect yourself against flu. It is available from October each year and starts to work about 2 weeks after you get it.
That 2-week gap matters in December. If you plan to visit older relatives or travel home for Christmas, getting vaccinated by early December gives your protection time to build. You can still get flu after vaccination, but symptoms are usually milder and recovery faster. You need a new vaccine every year, because flu strains change and protection fades.
In Ireland, the flu vaccine is recommended, and offered free, for people at higher risk. This includes people who:
- Are aged 60 or older
- Are aged 2 to 17 (children get a nasal spray rather than an injection)
- Are pregnant, at any stage
- Are aged 6 months or older and have a long-term condition such as chronic heart, lung, kidney, liver or neurological disease, diabetes, or a weakened immune system
- Live with, or care for, someone with one of those conditions
- Are healthcare workers, live in a nursing home or long-term care facility, or have regular contact with pigs, poultry or waterfowl
Do not get the vaccine while you have a temperature of 38 degrees or above; wait until you are well. If you have had a severe allergic reaction to a previous flu vaccine, you should not have it. Most people with an egg allergy can still be vaccinated. Mild side effects such as a sore arm, headache or a slight temperature are common and pass quickly.
Not sure whether you are in a risk group, or whether the vaccine suits your health condition or pregnancy? Our doctor can talk it through with you by video and advise.
Online care
How our online doctor can help with flu
Most of a flu assessment is a careful history, which works well over a secure video call.
Our Same-Day Online Doctor Consultation is a 15-minute secure video call for €39 with an Irish-registered doctor. Same-day slots are available. The doctor will:
- Assess your symptoms: when they started, how they are changing, and your age, pregnancy status and health conditions.
- Check for red flags: signs of pneumonia, dehydration or other complications that need urgent in-person care.
- Agree a plan: symptom relief, how long to stay off work and away from vulnerable relatives, and what to watch for.
- Advise on the flu vaccine for you and your family, including risk groups and pregnancy.
- Issue documentation, such as a medical certificate, when clinically appropriate and at the doctor's discretion.
- Arrange next steps: referral for tests, imaging or specialist review where clinically indicated.
Please note that electronic sick leave certificates are not accepted by the Department of Social Protection, and backdated notes are not routinely issued. Some problems, such as listening to the chest, need an in-person examination; if so, the doctor will tell you clearly and direct you to the right service.
Care in Ireland
Talk to a doctor about flu
A video consultation with an Irish-registered doctor can help you understand your symptoms, spot complications early and agree a plan for the days ahead.
Flu not settling, or worried about a relative?
Talk through your symptoms with an Irish-registered doctor by secure video, often the same day, and leave with a clear plan.
Sources
Evidence behind this article
Sources checked on 8 November 2026.
Symptom timings come from ECDC and a review of volunteer challenge studies in healthy adults; children and older people may follow a different course. Vaccine eligibility and treatment points reflect Irish national guidance reviewed between December 2025 and September 2026. National influenza surveillance reports were paused in October 2026, so this article gives no current-season case numbers.
Questions
Common questions about flu
How long does flu last in adults?
Usually 3 to 7 days, with the worst symptoms in the first 2 to 3 days. Tiredness can last up to 2 weeks and a dry cough 3 weeks or more. People with a weakened immune system can be ill for longer.
How long am I contagious with flu?
You can pass flu on shortly before symptoms start, and you shed the most virus in the first few days. Stay away from others until 48 hours after your symptoms improve, and avoid visiting vulnerable relatives, nursing homes and hospitals in that time.
When should I get the flu vaccine before Christmas?
As early in the season as you can. The vaccine is available from October and takes about 2 weeks to work, so getting it by early December gives you protection before family gatherings and travel.
Will antibiotics or antivirals help me get over flu faster?
Antibiotics do not work against flu. Current Irish guidance does not recommend antivirals for non-severe flu, including in higher-risk groups; they are kept for severe illness, usually in hospital. Rest, fluids and paracetamol are the main treatment.
Can I get a medical certificate for flu online?
Our doctor may issue a medical certificate when clinically appropriate, after assessing you by video. Electronic sick leave certificates are not accepted by the Department of Social Protection, and backdated notes are not routinely issued.
