Sputum: Definition, Causes, Common RTIs, Recommendations and Available Tests

It occurs when a person’s lungs are diseased or damaged. It is a thick mucus, sometimes called phlegm, expelled from the lungs.

The body produces mucus to keep the thin and delicate tissues of the respiratory tract moist so that tiny particles of foreign matter that may pose a threat can be trapped and expelled.

Sometimes, like when there is an infection in the lungs, excess mucus is produced. The body tries to get rid of this excess by coughing it up like sputum.

Sputum is a type of mucus that can be expelled when you cough. There are many different reasons for the body to produce excess sputum.


Below is a list of some of these causes, along with the way sputum can appear:


In smokers, mucus builds up in the lungs and causes a “smoker’s cough.” The sputum produced can be green, yellow, or bloody.

Asthma :

People with asthma have airways sensitive to allergens, environmental pollution, and respiratory infections. This sensitivity can cause inflammation of the airways and an increase in mucus production.


Cystic fibrosis:

Cystic fibrosis is a hereditary disease caused by a defective gene. It leads to the smaller airways becoming blocked with thick mucus, which causes breathing difficulties.

The thick mucus in cystic fibrosis becomes an ideal environment for bacteria to grow. Many people with cystic fibrosis develop chronic bacterial pulmonary infections.

Respiratory tract infections (RTI):

Sputum that is a different color from saliva may signify a lower RTI. With bacterial RTIs, sputum can also have a thick consistency and an unpleasant odor.

Generally, sputum is dark green in the early stages of infection and gradually lightens as the condition improves.

It is the presence of an enzyme called myeloperoxidase that gives the sputum its green color during an infection.

Some infections can make the sputum yellow, gray, or rusty.

RTI common


The flu or the flu can cause green phlegm. The main symptoms are:

  • High temperature, 100.4 ° F or more.
  • Fatigue.
  • Weakness.
  • Headache.

Other common symptoms include general aches and pains, convulsive cough, and cold-like symptoms, such as stuffy or runny nose, sneezing, and sore throat.

People should rest at home, drink plenty of water, and stay warm. Over-the-counter painkillers will help when someone has the flu, and most people will start to feel better in a week.

If it starts within two days of becoming sick, antiviral medications such as oseltamivir can reduce the time a person is suffering for 1-2 days.

Taking antiviral medications later in the infection can also be beneficial, especially if someone is sick or has a high risk of developing complications.


Bronchitis is an infection of the lung’s central airways, the bronchi, which become inflamed and produce extra mucus. People with this condition can cough yellowish or greenish-gray sputum. Bronchitis is a lung condition that can be acute or chronic.

Acute bronchitis lasts about three weeks. Chronic bronchitis is defined as a daily cough that produces sputum and lasts for at least three months and occurs for two consecutive years. It is a symptom of other lung conditions, such as emphysema and chronic obstructive pulmonary disease (COPD).

Most cases of acute bronchitis can be treated at home with nonsteroidal anti-inflammatory drugs (NSAIDs) and drinking lots of fluids.

Pneumonia :

A cough that produces thick yellow, green, brown, or blood-stained sputum can be a sign of pneumonia, a bacterial infection that leads to swelling of lung tissue.

Some common symptoms of pneumonia include:

  • Difficult breathing
  • Rapid heartbeat
  • Fever.
  • Feeling generally bad
  • Sweat and shake.
  • Loss of appetite

If you think you have pneumonia, you should see a doctor.

Tuberculosis (TB):

If someone has TB, they can expectorate bloody or green phlegm. They will also experience symptoms that may include:

  • Weightloss.
  • Night sweats.
  • Fever.
  • Fatigue.
  • Loss of appetite
  • Swelling in the neck

Tuberculosis is a severe disease, but it can be treated with a 6-month course of antibiotics.

Although TB ​​is a bacterial infection that primarily affects the lungs, it can also affect the upper body, glands, bones, and nervous system.


Sputum may indicate an RTI, which will require medical attention in some cases. Anyone who suspects that they have TB should seek medical attention and receive treatment.

If someone thinks they may have pneumonia, they should also talk to a doctor. The condition can be challenging to diagnose because it shares symptoms with other common ITRs. Mild pneumonia can be treated at home with antibiotics, rest, and plenty of fluids.

Most of the other RTIs will resolve themselves over time. Doctors recommend taking over-the-counter pain relievers, drinking plenty of fluids, and resting.

However, there will be times when it is best to seek medical attention. These occasions include when someone has a severe cough that lasts more than three weeks.

If someone has a temperature of more than 100.4 ° F for more than three days, this can be a sign of pneumonia, so it is essential to see a doctor.

If a person coughs up a blood-spattered mucus, breathes quickly, develops chest pains, or becomes numb or confused, they should go to the doctor.

The same is true for anyone who has an underlying heart or lung condition or experienced repeated bronchitis episodes.

What is a sputum culture test?

If someone visits a doctor, you may be asked to have a sputum culture test. This test is used to diagnose bacterial pneumonia or bronchitis. It can also control how the treatment works for a particular condition.

The sputum culture test is usually done with a Gram stain, identifying the bacteria causing the infection. Specialized tests can also be done if the Gram stain can not detect the bacteria that cause the disease.

These include a smear and culture of AFB to find tuberculosis and non-tuberculous mycobacteria, a fungal culture, or a Legionella culture.

A sputum sample will usually be collected early in the morning. Depending on the infection in question, up to three more examples can be taken in the following days.

When sending for a sputum test, people may be asked to wash their teeth, rinse their mouths with water and avoid food 1-2 hours before.

To produce a sample of the lungs, the person is usually asked to cough deeply. If someone can not cough up sputum, you may be asked to inhale a sterile saline or glycerin solution to loosen the phlegm in the lungs. Vapor inhalation can also be used sometimes.

In addition to a sputum culture test, a doctor may request that someone have a complete blood count to detect any other signs of illness.