Usually not. Yellow or green phlegm is common with an ordinary cold or chest infection, and the colour on its own does not mean you need antibiotics. Most of these infections are caused by viruses, which antibiotics cannot treat.
The short answer
- Yellow or green phlegm does not, by itself, mean you have a bacterial infection.
- Antibiotics do not work on viruses, which cause colds, flu and most chest colds.
- Most chest infections clear up on their own. The worst is usually over in 7 to 10 days, though the cough and phlegm can last up to 3 weeks.
- See a doctor if the cough lasts more than 3 weeks, you cough up blood, you are short of breath, or you are getting worse.
What does yellow or green phlegm mean?
It means your airways are irritated or infected, which happens with colds, flu and chest infections. A chesty cough that brings up yellow or green phlegm is one of the main symptoms of a chest infection. It tells you that you are ill. It does not tell you whether a virus or bacteria is the cause.
When do antibiotics help?
Antibiotics only work against bacteria. A doctor will prescribe them for a bacterial chest infection or for pneumonia, and may prescribe them if you are at higher risk of complications.
They do not help with:
- colds and runny noses, even when the mucus is thick, yellow or green
- flu
- most chest colds (acute bronchitis)
- most sore throats
Why not take antibiotics just in case?
Antibiotics will not make you feel better if a virus is the cause, and they are not harmless. Side effects include rash, nausea, diarrhoea and yeast infections. Less often they cause severe allergic reactions or a serious bowel infection called C. diff.
Every time antibiotics are used, bacteria get another chance to become resistant to them. That makes future infections harder to treat, for you and for everyone else.
What is the best antibiotic for yellow phlegm?
There is no antibiotic to choose for yourself. If you need one, your doctor will pick it based on the type of infection and your medical history. Do not take antibiotics left over from an earlier illness or prescribed for someone else.
What helps while you recover
- Get plenty of rest.
- Drink lots of water. It helps to loosen the phlegm.
- Raise your head with extra pillows when you sleep.
- Take a painkiller such as paracetamol for fever, headache or aching muscles.
- Try a warm drink of lemon and honey to soothe your throat. Do not give honey to babies under 1 year.
- Do not smoke.
When to see a doctor
- Your cough has lasted more than 3 weeks.
- You are coughing up blood or blood-stained phlegm.
- Your symptoms are getting worse, not better.
- You have had a fever for more than 5 days.
- You are pregnant, over 65, have a weak immune system or have a long-term condition such as heart, lung or kidney disease.
A cough that lasts more than 3 weeks, especially with night sweats, weight loss or tiredness, should also be checked for tuberculosis (TB). TB is curable with the right treatment. See our guide to conditions that start with a cough.
When to get urgent medical help
Go to your nearest emergency unit or call an ambulance if you:
- are struggling to breathe
- have lips or skin turning blue, grey or very pale
- have chest pain
- become suddenly confused
This article is general information and does not replace advice from your own doctor. If you are worried about a cough, make an appointment with your GP.
Medically reviewed by the ASAIPA clinical team.
