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Your cold is long gone, but the cough is still hanging around.
By week three, most people shrug and assume it will fade soon.
But a cough that lasts more than 3 weeks isn’t always a cold hangover. It may be time for chronic cough tests.
This guide covers what doctors usually check first, what comes next, and which clinic to visit in Korea.
Quick summary: Chronic cough tests usually begin with a medical history and a chest X-ray.
If the X-ray looks normal, doctors check common causes such as asthma, reflux, and postnasal drip one by one.
A local internal medicine clinic or a pulmonology (lung) clinic is a good starting point.
What chronic cough tests will I get after a cough lasts 3 weeks?
Most doctors start with your history, a chest exam, and a chest X-ray.
The Korean Academy of Tuberculosis and Respiratory Diseases cough guideline puts the chest X-ray first for a cough lasting 3 weeks or more.
Chronic cough is a cough that lasts more than 8 weeks.
Under 3 weeks is acute, and 3 to 8 weeks is subacute.
The approach changes with duration, so check which group your cough falls into.
| Type | Duration | Usual approach |
|---|---|---|
| Acute cough | Under 3 weeks | Often an infection such as a cold; doctors often watch how it progresses |
| Subacute cough | 3 to 8 weeks | History, exam, and a chest X-ray |
| Chronic cough | 8 weeks or more | Chest X-ray, then step-by-step checks for common causes (upper airway, asthma, reflux) |
The UK’s NHS also advises seeing a GP (general practitioner) if a cough lasts more than 3 weeks.
Source: Korean Academy of Tuberculosis and Respiratory Diseases, “2020 Revised Cough Clinical Practice Guideline” (2020); NHS, “Cough” (checked October 2026)
Past 3 weeks, a cough moves from “wait and see” to “find the cause.” The first test is usually a chest X-ray.
What does a chest X-ray show in chronic cough?
It screens for major problems in the lungs themselves, such as pneumonia, tuberculosis, or a tumor.
A chest X-ray is a basic imaging test that uses a low dose of radiation to show the lungs, heart, and rib cage in one image.
It’s quick, and most clinics can do it on the spot.
Here are the main clues doctors look for.
- Shadows that may suggest pneumonia or other inflammation
- Lesions that may suggest tuberculosis
- Nodules or masses that may suggest a lung tumor
- Heart-related clues, such as an enlarged heart or fluid in the lungs
An X-ray can’t easily show the most common causes, though. These include postnasal drip, acid reflux, and asthma.
Asthma and chronic bronchitis can even show up with a normal X-ray.
Source: Mayo Clinic, “Chronic cough – Diagnosis and treatment” (checked October 2026)
A normal X-ray mostly means no major lung disease stands out. It doesn’t mean there’s no cause. If the cough continues, talk with your doctor about the next tests.
A cough lasting 2 weeks or more is also known as a possible sign of tuberculosis.
In that case, you’d get a chest X-ray plus a sputum (phlegm) test for TB bacteria.
If you also have fever, night sweats, or weight loss, get checked sooner.
Source: Mokpo City Public Health Center, “Tuberculosis Information > Pulmonary TB” (checked October 2026)
Which chronic cough tests come next if the X-ray is normal?
Doctors check the three common causes one at a time: upper airway cough syndrome, asthma, and gastroesophageal reflux disease (GERD).
Your symptoms and exam findings decide which test comes first.
| Test | What it checks | Usually linked to |
|---|---|---|
| Lung function test (spirometry) | How much air you blow out, and how fast | Asthma, COPD |
| Methacholine challenge | How sensitive your airways are (sometimes used when spirometry is normal) | Cough-variant asthma |
| Sputum test (including induced sputum cytology) | Germs and inflammatory cells | Infections such as TB, eosinophilic bronchitis |
| Sinus exam or sinus CT | Sinus inflammation | Upper airway cough syndrome |
| Esophageal pH monitoring | Acid reflux | GERD |
| Chest CT | Finer detail of lung structure | Chosen when the X-ray is abnormal or more detail is needed |
Your medicines can cause a cough too.
Some blood pressure drugs (ACE inhibitors) are known to be linked to a dry cough.
Don’t stop any medicine on your own. Talk to the doctor who prescribed it.
China’s 2021 cough guideline suggests this: if 4 weeks of trial treatment for common causes doesn’t help, get tested at a hospital that can find the cause.
It also doesn’t recommend chest CT as the first test for a newly seen chronic cough.
Source: Korean Academy of Tuberculosis and Respiratory Diseases, “2020 Revised Cough Clinical Practice Guideline” (2020); AAFP, “Evaluation of the Patient with Chronic Cough” (2011); Chinese Thoracic Society Asthma Group, “Guideline for the Diagnosis and Treatment of Cough (2021)” (2022)
Which doctor should I see for a cough that won’t go away?
A pulmonology clinic or a nearby internal medicine or family medicine clinic is the usual starting point.
If nose, throat, or reflux symptoms stand out, you may be seen by other specialists too.
- Internal medicine or family medicine clinic: an easy first stop for a consultation and chest X-ray
- Pulmonology: lung function tests and assessment of asthma, COPD, and lung disease
- ENT (ear, nose, and throat): postnasal drip, stuffy nose, or a lump-in-the-throat feeling
- Gastroenterology: sour taste, heartburn, and other reflux symptoms
In Korea, large “tertiary” hospitals often ask for a referral letter (진료의뢰서) from a local clinic. This helps you get coverage under National Health Insurance (Korea’s public health insurance).
Check with the hospital before you go.
☐ The date your cough started and how long it has lasted
☐ Dry cough, or with phlegm
☐ Worse at night, early morning, or after exercise
☐ Medicines you take (including blood pressure drugs)
☐ Smoking history and dust exposure at work
☐ Fever, night sweats, or weight loss
If you cough up blood, have trouble breathing, have chest pain, or your cough gets suddenly worse and you feel very unwell, don’t wait. Get medical care right away. (Based on NHS advice)
For more on preparing for exams, see our Exams & Procedures Guide. (Internal link: replace with a related article after publishing)
Frequently Asked Questions
1. My cough passed 3 weeks. Should I get a CT scan right away?
Usually, a chest X-ray comes first. China’s guideline also doesn’t recommend CT as the first test for a newly seen chronic cough. Your doctor may add a CT if the X-ray is abnormal or more detail is needed.
2. Is a cough that lasts
longer than 3 weeks after a cold normal?
Sometimes a cough lingers for 3 to 8 weeks after an infection. Other causes can overlap, though, so it’s safer to get checked once it passes 3 weeks.
3. Do I need tests for a dry cough with no phlegm?
Yes, it can be worth it. A dry cough can come from asthma, acid reflux, or medicines. If it lasts 3 weeks or more, talk with a doctor whether or not you bring up phlegm.
4. Should I get a TB test if my cough passes 2 weeks?
A cough lasting 2 weeks or more is known as one possible sign of tuberculosis. If you also have fever, night sweats, or weight loss, ask your doctor about a chest X-ray and a sputum test.
References
1. (Korean Academy of Tuberculosis and Respiratory Diseases), “2020 Revised Cough Clinical Practice Guideline” (2020 개정 기침진료지침), 2020 Link
2. (European Respiratory Society), “ERS guidelines on the diagnosis and treatment of chronic cough in adults and children”, 2020 Link
3. (Mayo Clinic), “Chronic cough – Diagnosis and treatment”, checked October 2026 Link
4. (NHS), “Cough”, checked October 2026 Link
5. (American Academy of Family Physicians), “Evaluation of the Patient with Chronic Cough”, 2011 Link
6. (Chinese Thoracic Society Asthma Group), “Guideline for the Diagnosis and Treatment of Cough (2021)” (咳嗽的诊断与治疗指南(2021)), 2022 Link
7. (Japanese Respiratory Society), “Guidelines for the Management of Cough and Sputum, 2nd Edition 2025” (咳嗽・喀痰の診療ガイドライン第2版2025), 2025 Link
8. (Mokpo City Public Health Center), “Tuberculosis Information > Pulmonary TB” (결핵정보 > 폐결핵), checked October 2026 Link
This article is for general informational purposes only and is not a substitute for professional medical advice, diagnosis, or treatment. Please consult a qualified healthcare provider if you have health concerns.
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