More phlegm, or phlegm that has changed: the colour is not really the point, the change is
Division of Pulmonary Medicine, Taipei Veterans General Hospital Hsinchu Branch · Symptom triage
Related pagesFind your symptomA cough that won’t go awayCOPD
Three sentences first
- Phlegm turning yellow or green does not mean a bacterial infection, and it is not a reason to take an antibiotic. The colour comes from an enzyme inside white blood cells, and a virus or an allergy will change the colour just as readily.
- What does mean something is “what is different from usual” — more of it, thicker, with fever or breathlessness as well.
- Blood in the phlegm is a separate matter. However little there is, it needs to be seen by a doctor, and in Taiwan tuberculosis, bronchiectasis and lung cancer have to be ruled out first.
🚩 With any of these, see a doctor as soon as you can
- Blood in the phlegm, or coughing up blood — even if it is only a streak. More than half a bowl at once, or repeatedly over a short period, is an emergency: go to hospital immediately.
- A sudden large increase in the amount of phlegm, with a clear change in colour and smell, together with fever or increasing breathlessness.
- Foul-smelling phlegm — this may be an anaerobic infection or a lung abscess.
- Unexplained weight loss, or night sweats, together with long-standing phlegm.
- Repeated pneumonia in the same place (twice or more).
- Chronic lung disease (COPD, bronchiectasis) and this episode is not like the previous ones.
- Phlegm and fever starting after choking on something, particularly in an older person or anyone whose swallowing is not good.
If you are coughing up blood, keep one lot of the phlegm to show your doctor (or photograph it), and note down the colour, roughly how much and how many days. Those details help the assessment a great deal.
What does the colour of phlegm actually mean?
This is the question asked most often in clinic, and the one most often misunderstood.
| Colour / character | What it usually means | What to watch for |
|---|---|---|
| Clear, white, sticky | Ordinary airway secretions, common in allergy, postnasal drip and the early stage of a viral infection | A sudden increase in the amount still matters |
| Yellow, green | The result of white blood cells gathering — viruses, bacteria and allergic inflammation all do this | The colour cannot be used to decide whether to take an antibiotic |
| Rust-coloured | Classically seen in pneumococcal pneumonia | Usually with a high fever and chest pain; see a doctor |
| Pink, frothy phlegm | Pulmonary oedema (acute heart failure) | An emergency; with severe difficulty breathing, call an ambulance at once |
| Streaked with blood, or bright red | Bleeding from the airway lining, bronchiectasis, tuberculosis, lung cancer | Any amount needs a doctor |
| Black | Inhaled soot, severe air pollution, smoking; rarely a fungal infection | With fever or weight loss, it needs further investigation |
| Foul-smelling, separating into layers | Anaerobic infection, lung abscess, severe bronchiectasis | Needs imaging and culture of the phlegm |
Remember one principle: what your doctor cares about is the “change”, not the “colour”. If your phlegm is always yellow and it is still yellow this week, that means little. If you usually bring up clear phlegm and this week it has suddenly become thicker and more plentiful, with a fever as well, that means something.
What might be causing long-standing phlegm?
Postnasal drip (upper airway cough syndrome)
Strong evidenceMany people think they have “a lot of phlegm” when in fact the secretions are coming from the nose, not the lungs. Secretions from the sinuses run back into the throat, and when they are cleared they look just like phlegm.
Clues: frequent throat clearing, a feeling of something in the throat, a blocked or running nose, worst on waking and on lying down, a history of nasal allergy. Treat the nose and the phlegm halves.
Chronic bronchitis
Strong evidenceThe definition is quite precise: cough and phlegm for at least three months a year, for two years running, with other causes excluded. The commonest background to it is smoking.
Clues: most phlegm in the morning, smoking or long-term exposure to cooking fumes. It overlaps heavily with COPD, so lung function testing is needed to see whether there is airflow obstruction as well.
Bronchiectasis
Strong evidenceRepeated infection leaves the bronchi permanently widened and distorted, the cilia no longer clear them, and phlegm collects inside; the collected phlegm then invites further infection, and a vicious cycle sets in.
Clues: phlegm every day and a large volume of it, repeated pneumonia in the same place, occasional blood in the phlegm, a past history of tuberculosis, whooping cough or severe pneumonia. An ordinary X-ray cannot show it; it needs an HRCT.
Chronic obstructive pulmonary disease (COPD)
Strong evidencePhlegm and airflow obstruction together. The point is that among people with phlegm, a proportion already have COPD without knowing it — and the earlier COPD is dealt with, the greater the difference in how fast the lungs decline.
Clues: aged over 40, a history of smoking, a morning cough with phlegm, progressively more breathless on exertion. Lung function testing is required to confirm it.
Tuberculosis
Must be ruled outTaiwan is still a country with an intermediate tuberculosis burden. A cough with phlegm lasting more than three weeks is itself a screening indicator, and early tuberculosis may cause no fever at all.
Clues: cough > 3 weeks, blood in the phlegm, weight loss, night sweats, poor appetite, a contact history. Sputum tests plus a chest X-ray are the standard approach.
Asthma
Strong evidenceAsthma is not only breathlessness — it can also produce sticky phlegm that is hard to cough up. There is a form, eosinophilic asthma, that responds particularly well to inhaled corticosteroids.
Clues: coming and going, worse at night or in the early morning, wheezing, an allergic constitution. A raised FeNO is a useful clue.
Gastro-oesophageal reflux
ModerateThe irritation of reflux increases airway secretions, and it can also make you feel as though there is phlegm in your throat the whole time (laryngopharyngeal reflux).
Clues: worse after meals or on lying down, a sour or burning taste in the throat, hoarseness, and heartburn is not always present.
Aspiration (particularly in older people)
Strong evidenceWhen swallowing is failing, saliva or food gets into the airway quietly (silent aspiration), causing chronic phlegm and repeated pneumonia. This is very common in older people after a stroke, and in dementia and Parkinson’s disease.
Clues: choking on food, choking particularly easily on water, a wet-sounding voice while eating, repeated pneumonia, weight loss. A swallowing assessment is needed, not just treatment of the pneumonia.
Lung cancer
Must be ruled outA tumour obstructing a bronchus causes secretions to stagnate beyond it and infection to recur. Repeated pneumonia in the same place is an important warning sign.
Clues: blood in the phlegm, repeated pneumonia in the same place, weight loss, hoarseness, lung cancer in a first-degree relative.
Which tests are usually done?
It answers: is there pneumonia, tuberculosis, a mass or fluid? The first step in long-standing phlegm.
It answers: is this tuberculosis? Which organism is it? Essential when a cough with phlegm has lasted more than three weeks, or when there is blood in the phlegm.
Please provide phlegm coughed up from deep down rather than saliva — a saliva sample has very little diagnostic value. The first phlegm of the morning is usually of the best quality.
It answers: is there bronchiectasis? This is the only reliable tool for it, and an X-ray cannot show it. It is also used to assess the cause of repeated pneumonia.
This is a second-line test. A large volume of phlegm every day, repeated pneumonia in the same place, or a past history of tuberculosis or whooping cough usually meets the indications; but the National Health Insurance (NHI) requires the results of basic tests such as a chest X-ray first — see the explanation below.
It answers: is there airflow obstruction as well? Among people with long-standing phlegm, a proportion already have COPD without knowing it.
It answers: are these secretions in fact coming from the nose? A great deal of “too much phlegm” is really postnasal drip.
It answers: is there silent aspiration? Essential in older people and in anyone after a stroke, or with dementia or Parkinson’s disease, who has repeated pneumonia.
It answers: what is inside the airway? Arranged when no cause can be found for coughing up blood, when pneumonia recurs in the same place, or when imaging shows a suspicious lesion.
Samples can be taken directly for testing, and bleeding can be treated locally at the same time.
About CT of the chest: in Taiwan it is not a test you can simply ask for
CT has a high diagnostic value, but the strength of the evidence and whether the NHI will pay for it are two different things. In Taiwan it is governed by fairly explicit rules:
- It is second-line, not first-line. The NHI’s points to note in the review of medical expenses require the request form or the report for an imaging examination to state the clinical diagnosis, the purpose of the examination, the relevant history, the physical examination and the results of other relevant tests — which is to say that there usually has to be a chest X-ray first (with lung function testing and sputum tests if needed) that still does not explain things, before CT’s turn comes.
- There has to be a clear indication. The reviewers work out the purpose of the examination from the records. Simply wanting “a clearer look”, “to have a check-up while I am here” or “peace of mind” is not covered, and in that situation you usually pay out of pocket.
- Repeating it within a short period is reviewed strictly. Performing CT or MRI again within a short period (the rules give 12 weeks as the example) requires the clinical picture and the necessity to be set out in the records.
- The doctor has to look at the cloud images before ordering. Since 2019, if the images and reports uploaded for a patient in the previous 28 days have not been reviewed before CT or MRI is ordered in an outpatient clinic, that examination is not covered. So bringing your old reports, or saying clearly which hospital did them, is of real practical benefit to you.
So this page labels CT as Strong evidence Conditions apply: the diagnostic value is clear, but whether it is done and whether it is covered is for your doctor to judge from your clinical situation and the rules in force.
Based on: the clauses on imaging examinations in the Points to Note in the Review of National Health Insurance Medical Expenses, National Health Insurance Administration, Ministry of Health and Welfare, together with the NHI Administration’s rules on reviewing cloud images. The clauses are revised from time to time; what actually applies should follow the NHI Administration’s latest notices and the explanation given by your hospital or clinic.
What you can do for yourself
- Drink enough: when phlegm is too thick to cough up, topping up your fluids is more direct than any mucolytic (if you have been told to restrict fluids for heart or kidney disease, ask your doctor first).
- Learn to cough effectively: breathe in deeply, hold for two or three seconds, then cough twice using your abdomen. Far more effective than coughing lightly over and over, and gentler on the throat.
- Postural drainage: if you have bronchiectasis, find time each day to lie with the affected side uppermost, together with deep breathing and chest percussion, to help the phlegm out.
- Stop smoking: this is the only intervention that genuinely reduces the amount of phlegm and also slows the decline in lung function.
- Treat the nose at the same time: get nasal allergy and sinusitis under control and “the phlegm” often drops by well over half.
- Have your vaccinations: influenza and pneumococcal vaccines can reduce acute exacerbations and admissions to hospital.
- Do not keep antibiotics at home in reserve: the colour is not a basis for treatment, and taking them at random only breeds resistance, so that there is nothing left that works when you really need it.
Common questions
My phlegm is green and my doctor still will not prescribe an antibiotic. Is that not too cautious?
No. The yellow-green colour of phlegm comes from myeloperoxidase in white blood cells, so the colour changes whenever white cells gather — which happens in viral infection and in allergic inflammation too. A number of studies show that the colour of phlegm cannot reliably distinguish a bacterial from a viral infection. What your doctor judges by is the change in the amount of phlegm, whether there is fever, whether you are breathless, whether you have chronic lung disease, and what the X-ray says. An unnecessary antibiotic will not get you better any faster, but it will bring diarrhoea and resistance.
It is only a streak of blood. That should be all right, shouldn’t it?
It still needs a doctor. The commonest cause of coughing up a small amount of blood is in fact bronchitis or bleeding from the nasopharynx, and most of the time it is not serious — but early tuberculosis, bronchiectasis and lung cancer can also present as nothing more than a streak of blood. A chest X-ray and a sputum test cost you very little and can rule out precisely the conditions where early detection matters most. Do also check whether the blood was coughed up from below the throat, or came from the nose running back or from bleeding gums — your doctor will ask.
I spend ten or fifteen minutes clearing phlegm every morning. Is there anything to be done?
Yes, but the way forward is to find the cause rather than simply to take a mucolytic. First establish whether it is postnasal drip, chronic bronchitis, bronchiectasis or COPD — the four are managed in completely different ways. If it is bronchiectasis, regular airway clearance techniques (postural drainage, a positive expiratory pressure device) and treating the underlying cause do far more than medicines. The suggestion is to arrange a chest X-ray and lung function testing first; if those still do not explain things, and there is repeated infection or a large volume of phlegm, your doctor can then assess whether an HRCT is needed.
My elderly relative chokes on food. Is that connected with having a lot of phlegm?
Very much so. People whose swallowing is failing often have silent aspiration — saliva or food enters the airway without any obvious choking, causing chronic phlegm and repeated pneumonia. In that situation treating the pneumonia only treats the symptom: a swallowing assessment is essential, and only adjusting the texture of food, the posture for eating and mouth care will genuinely reduce the attacks. If an older relative has repeated pneumonia, raise this possibility with the doctor yourself.
How do I collect a phlegm sample properly?
The point is to collect real phlegm and not saliva. The advice is: after getting up in the morning, rinse your mouth first (not with mouthwash), then breathe in deeply and use your abdomen to cough it up from the lungs, spitting it straight into the container. If you cannot bring anything up, drink some warm water first, or let the steam of a hot shower help, or ask the staff to arrange a nebulised mucolytic to induce it. Testing for tuberculosis usually needs three sets, and the early-morning one is of the best quality.
What to do next
The single most worthwhile thing to do about long-standing phlegm is to settle the four questions — the nose, airway obstruction, bronchiectasis and tuberculosis — in one go. Usually one clinic visit plus a chest X-ray, lung function testing and sputum tests narrows most of it down.
References
- 衛生福利部疾病管制署. 結核病診治指引第七版. 臺北：疾病管制署. Available from: https://www.cdc.gov.tw
- Polverino E, Goeminne PC, McDonnell MJ, et al. European Respiratory Society guidelines for the management of adult bronchiectasis. Eur Respir J. 2017;50(3):1700629.
- 衛生福利部中央健康保險署. 全民健康保險醫療費用審查注意事項——影像檢查相關條文；門診開立電腦斷層／磁振造影前之醫療影像調閱規定. Available from: https://www.nhi.gov.tw
References follow the ICMJE (Vancouver) style. Guidelines and official documents are given with their version or year of publication; legislation and National Health Insurance (NHI) rules are given with the responsible authority and the version date. Last checked: 8 October 2026.
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