What Are the 4 Stages of Pneumonia?

The symptoms and complications of lobar pneumonia, a condition that affects one or more of the lobes of the lungs, can be broken down by stages into early findings and late findings.

This article discusses the progression or stages of pneumonia from early to late in people who receive treatment as well as in those who do not.

A healthcare provider using a stethoscope on an older person in a bedroom

FG Trade / Getty Images

Early Stage of Pneumonia

The symptoms of the first stage of pneumonia, or what you might expect in the first 24 hours, are very important to understand. When pneumonia is detected at this stage, and promptly treated, the severity of the disease and potential complications may be reduced.

Most commonly, lobar pneumonia begins suddenly with fairly dramatic symptoms. (Unlike bacterial pneumonia, however, viral pneumonia may have a gradual onset with milder symptoms.)

With pneumonia (in contrast to a condition such as bronchitis that primarily affects the larger bronchi), the tiniest airways of the lungs (the alveoli) are affected. Since this is where the exchange of oxygen and carbon dioxide takes place (between the alveoli and nearby capillaries), pneumonia may cause symptoms related to lower oxygen levels in the body. In addition, lobar pneumonia often extends to the membranes surrounding the lungs (the pleura), which can lead to particular symptoms.


Symptoms often occur abruptly in the earliest stage of pneumonia, and a person may appear quite ill. Symptoms may include:

  • A cough, which may be productive of sputum that is clear, yellow, or green. (It's important to note that the cough associated with pneumonia can appear similar or identical to the cough associated with other lung infections such as bronchitis.)
  • A high fever and chills (sometimes shaking chills)
  • Chest heaviness
  • Since the disease can spread to the pleura early, symptoms of pain with a deep breath (pleuritic chest pain) may occur.
  • Shortness of breath may occur as the alveoli fill with fluid, bacteria, and immune cells (replacing air).
  • Hypoxia, or a reduced oxygen level in the body
  • In some cases, symptoms of hemoptysis (coughing up blood) or cyanosis (a bluish tinge to the lips and fingers due to lack of oxygen) may occur, even at the onset of the infection.
  • A rapid respiratory rate (tachypnea): Respiratory rate is one of the most valuable signs that indicate the severity of the infection at the time of diagnosis.
  • A rapid heart rate (tachycardia)
  • Other symptoms such as a headache, loss of appetite, muscle aches (myalgia), joint aches (arthralgia), and fatigue
  • Nausea, vomiting, and/or diarrhea occur relatively often (in up to 20% of people with pneumococcal pneumonia), and can sometimes suggest that bronchitis or an upper respiratory infection has progressed to pneumonia.

Stage 1 Symptoms in the Elderly

In older adults, typical symptoms (such as a fever or cough) may be absent, and instead the only symptoms may be confusion or falls.

Management/Treating Symptoms

The most important step in the management of the earliest stage of pneumonia is prompt recognition. Symptoms that strongly suggest pneumonia (instead of a milder infection) include:

  • A high fever
  • Chills
  • A rapid respiratory rate
  • A rapid heart rate
  • A low oxygen level in the blood

With any of these symptoms, imaging—such as a chest X-ray—should be done.

Once diagnosed, antibiotics should be started almost immediately. Blood cultures (blood tests done to see if bacteria are present in the blood) are often done, and then antibiotic treatment started based on what your physician believes are the most likely causative organisms (empirical treatment).

Depending on the severity, hospital admission or intensive care unit (ICU) admission may be needed. This is especially true with an elevated respiratory rate, especially a breathing rate greater than 25 to 30 breaths per minute at rest. In the hospital, oximetry is usually used to monitor oxygen levels continually. Intravenous fluids may also be needed. If oxygen saturation is below 90% on oximetry, oxygen therapy may be needed, even this early in the infection.

When antibiotics are started promptly following early signs of infection, the fever may resolve within 48 to 72 hours after antibiotics are started.


The most common complication of early pneumonia (that may necessitate hospitalization) is a low oxygen level (hypoxia). Depending on the severity, oxygen supplementation may be needed, as well as admission to the ICU.

First Days of Pneumonia

After the initial 24 hours, symptoms of pneumonia may worsen and/or complications may occur as bacteria and immune cells fill the lungs and alveoli.


During the first few days of pneumonia (roughly the first three to four days), symptoms are usually more severe even if treatment has been started. These can include:

  • A cough that may become more productive (more sputum). The color and consistency of sputum may also change, becoming more yellow-green and thicker. It may also begin to take on a rust-like or even blood-tinged appearance.
  • Fever often continues, and with the immune system activated, shaking chills, rigors, and sweating may occur.
  • Shortness of breath may appear (or worsen if already present) as more fluid accumulates in the alveoli.
  • Associated symptoms such as headache and muscle aches often persist.
  • Lips and fingers may appear blue (cyanosis) or even take on a blackish appearance due to low oxygen.
  • Fatigue often worsens and becomes extreme.

In older adults, confusion or delirium may appear even if oxygen is being used.

The Importance of Respiratory Rate

The most useful sign as to severity at this stage is the respiratory rate (in people who do not have preexisting lung disease). A respiratory rate greater than 30 breaths per minute often means that hospitalization in intensive care is needed.

Managing/Treating Symptoms

During this stage of the infection, antibiotics are continued (intravenously if in the hospital), or started if a person has not yet been evaluated. For those diagnosed early, blood cultures may come back from the lab indicating the particular bacteria (if it is a bacterial pneumonia) responsible.

Knowing the type of bacteria present may lead physicians to change your treatment to a more appropriate or specific antibiotic. Sensitivities (tests that determine which antibiotic is most effective for the bacteria isolated) may also be returned and further guide appropriate therapy.

Oxygen may be started at this point or continued in those who already have low oxygen levels. In some cases, oxygen alone may be insufficient, A first step may be to use noninvasive positive pressure ventilation such as CPAP. Positioning may also help, as lying in the prone position (on your stomach) can maximize the surface area of the lungs available to absorb oxygen.

If low oxygen levels persist, or if there is evidence that organs of the body are not receiving enough oxygen (such as kidney dysfunction), insertion of an endotracheal tube and mechanical ventilation may be needed.

Additional testing may be needed if complications (see below) are suspected.


Complications may appear at any point with a diagnosis of lobar pneumonia, but this stage (the first few days after the initial diagnosis and treatment) is often when people appear most ill.


Bacteria that are present in the lungs may spread in the bloodstream (bacteremia) and thus travel to other regions of the body. With pneumococcal pneumonia, up to 25% to 30% of people will have bacteremia.

Bacteria traveling in the bloodstream can seed (lead to an infection beginning) in a number of other organs of the body. This may include:

  • The brain (meningitis)
  • Heart valves (endocarditis)
  • The lining of the heart (pericardium)
  • Joints (septic arthritis)
  • Kidneys
  • Spleen

Septicemia and Sepsis

Septicemia and/or sepsis may also occur (though are sometimes present at the onset of the infection) and are a significant cause of bad outcomes. While bacteremia refers to the presence of bacteria in the bloodstream, septicemia refers to a state in which bacteria are multiplying in the bloodstream. It is also sometimes called blood poisoning. In addition to typical symptoms of pneumonia, the presence of septicemia often results in a person appearing extremely ill with a very rapid pulse and confusion.

In contrast to septicemia, sepsis (or septic shock) refers to the body's response to the presence of bacteria in the bloodstream. This overwhelming response of the immune system is very critical, and, even with medications to raise blood pressure (which is often very low) and counteract the intense inflammatory response, can often be fatal. Significant research is focusing on ways to prevent this response from occurring.


An empyema may occur at any time during the course of pneumonia, but is usually not noted until a few days have passed. Since lobar pneumonia often extends to the lung linings (pleura), inflammation can result in the buildup of fluid between these membranes (a pleural effusion).

In some cases, pus may build up and accumulate between the pleural membranes, a complication known as an empyema. The most common causes include Streptococcus pneumoniae (the most common cause of bacterial pneumonia) and Staphylococcus. Symptoms are similar to pneumonia itself, with a cough, fever, chest pain, and shortness of breath, so doctors must be alert for this complication. If a significant pleural effusion is seen on imaging, further workup is often needed.

When an empyema is present, a thoracentesis is often the next step. This involves inserting a long, thin needle through the skin and into the pleural space to obtain a sample of the fluid. The sample can then be looked at in the lab to visualize any bacteria present and to do a culture of the fluid.

If a large empyema is present, a chest tube may need to be placed. This involves inserting a somewhat larger tube into the pleural space that is left in place and connected to continuous suction to remove the fluid.

In children, especially those who have pneumonia due to Staphylococcus aureus, an empyema may occur. Severe infections may also result in the collapse of the lung (pneumothorax) and pneumatoceles (air-filled cysts within the lungs).

As Pneumonia Progresses (Later in the First Week)

Later in the first week after a diagnosis of pneumonia, symptoms may again change and additional complications may occur.


Later in the first week after a diagnosis of pneumonia, symptoms can vary based on:

  • How soon the infection was diagnosed and treated
  • The age of the person
  • The particular organism (e.g., type of bacteria)
  • The severity of the initial infection

For some people, symptoms will be improving (but still persist to at least some degree as immune cells are still present).

For others, symptoms may continue to worsen (particularly in older people) and change. This may include:

  • Increased difficulty with breathing, and some people who were breathing on room air may require the addition of oxygen at this time (or other measures, including mechanical ventilation)
  • Coughing up blood

Managing/Treating Symptoms

During this stage of pneumonia, antibiotics (for bacterial pneumonia) will be continued. For those who are improving and in the hospital, intravenous antibiotics may be exchanged for oral antibiotics.

If complications have occurred, treatments to address these complications may continue, such as a chest tube to manage an empyema and corticosteroids if an intense immune response is present.

Oxygen or other types of breathing assistance may continue, be stopped, or instead be initiated for the first time.

For those who are hospitalized, attention to other complications, such as dehydration, kidney dysfunction, and more, will require careful monitoring and management.


Complications noted in the earlier stages of pneumonia may not occur until later in the first week for some people, especially those who have not received treatment.

For those who have a severe infection, a lung abscess may form.

In addition to symptoms associated with pneumonia—such as fever and cough—other symptoms of a lung abscess can include:

  • An increase in sputum (can become foul-smelling)
  • If the cough and fever had been improving, these may worsen again.
  • Night sweats (drenching sweats that require getting up and changing pajamas) can occur.
  • Weight loss in those who develop an abscess some time after their pneumonia occurred
  • Coughing up blood is also quite common.

An abscess itself can also lead to further complications, such as:

  • An empyema (if not already present)
  • A bronchopleural fistula (an abnormal passageway between the bronchi and the pleural cavity)
  • Bleeding into the lungs, and more

Treatment begins with broad-spectrum antibiotics (a lung abscess will usually require a change in antibiotics being used). If this is ineffective, the abscess may need to be drained (often with a long, narrow needle inserted through the skin). In some cases, surgical removal of the abscess will be needed. Follow-up is also very important, as underlying lung cancer has been found in one to two out of 10 lung abscesses.

Late-Stage Pneumonia

The final stage of lobar pneumonia (resolution of the infection) depends on how quickly treatment was started. Ordinarily, resolution of the infection occurs around eight days after the start of the infection. This recovery stage includes:

  • Resolution of the infection
  • Restoration of the normal airways and alveoli

At this point in the infection, the immune system works to repair the damage to the lungs. This includes the release of enzymes that break down damaged tissue so that it can be reabsorbed and the influx of cells (macrophages) that travel through the lungs and "eat" (phagocytize) debris and white cells containing bacteria.

Leftover debris in the lungs that can't be eliminated in this way is usually coughed up.


Since debris in the lungs that can't otherwise be removed is coughed up, a cough productive of sputum is very common at this stage. Knowing that the body is continuing to repair damage that was done during the infection can help explain the fatigue often present (and why rest is still important).

If untreated (and in some cases even with treatment), respiratory symptoms may worsen, When treatment is started early, however, and no serious complications have occurred, symptoms usually improve significantly at this point in time (except for the cough).

If scar tissue develops in the pleura (pleural adhesions), pain with a deep breath may occur, and may last for quite some time.

Managing/Treating Symptoms

Antibiotics are usually continued for at least 10 days, but if previously given intravenously, may be changed to oral tablets. For those who were hospitalized, many can be discharged (if not discharged already).

For those who continue to worsen, oxygen or mechanical ventilation may need to be started at this time. Very often, however, supplemental oxygen (or assisted breathing) may be able to be weaned. That said, some people will require continuous oxygen therapy, and in some cases, this will be needed long-term.


Complications discussed at other stages may occur later in the infection, especially lung abscesses (those are much less common than in the past).

The repair process may result in scar tissue in the lung linings (pleural adhesions) that may affect care in the future (it could cause problems with pleural effusions or lung cancer surgery in the future).

Roughly 10% to 15% of people will have a recurrent episode of pneumonia within two years of the infection.

For some people, lung damage may persist, requiring long-term oxygen supplementation. Severe pneumonia may also worsen underlying chronic obstructive pulmonary disease (COPD).


There are several "stages" of lobar pneumonia—which affects one or more of the lobes of the lungs—based on the time from the onset of the infection and the severity.

A Word From Verywell

Talking about the different stages of lobar pneumonia and potential complications can be frightening. That said, with prompt and effective treatment, the majority of people will recover without lasting symptoms or concerns.

In order to make sure you are treated as quickly as possible, it's important to be aware of possible symptoms of pneumonia and to call a healthcare provider with any warning signs. Perhaps the most important warning sign, however, is your "gut feeling." Trust your judgment. You've been living in your body a long time and know better than anyone else when it's telling you to be concerned. Trust your instinct.

8 Sources
Verywell Health uses only high-quality sources, including peer-reviewed studies, to support the facts within our articles. Read our editorial process to learn more about how we fact-check and keep our content accurate, reliable, and trustworthy.
  1. Reynolds JH, McDonald G, Alton H, Gordon SB. Pneumonia in the immunocompetent patient. Br J Radiol. 2010;83(996):998-1009. doi:10.1259/bjr/31200593

  2. American Lung Association. Pneumonia symptoms and diagnosis.

  3. Jameson JL, Fauci AS, Kasper KL, et al (Eds.). Harrison's Principles of Internal Medicine. McGraw-Hill Education.

  4. Floeystad HK, Berlin JD, Brandsaeter BJ, et al. Gastrointestinal symptoms in invasive pneumococcal disease: a cohort study. BMC Infect Dis. 2020;20(1):479. doi:10.1186/s12879-020-05211-3

  5. Centers for Disease Control and Prevention. Pneumococcal disease. Clinical features.

  6. Garcia-Vidal C, Ardanuy C, Tubau F, et al. Pneumococcal pneumonia presenting with septic shock: host- and pathogen-related factors and outcomes. Thorax. 2010;65(1):77-81. doi:10.1136/thx.2009.123612

  7. Godfrey MS, Bramley KT, Detterbeck F. Medical and surgical management of empyema. Semin Respir Crit Care Med. 2019;40(3):361-374. doi:10.1055/s-0039-1694699

  8. Kuhajda I, Zarogoulidis K, Tsirgogianni I, et al. Lung abscess-etiology, diagnostic and treatment options. Annals of Translational Medicine. 2015. 3(13):183. doi:10.3978/j.issn.2305-5839.2015.07.08

Additional Reading

By Lynne Eldridge, MD
 Lynne Eldrige, MD, is a lung cancer physician, patient advocate, and award-winning author of "Avoiding Cancer One Day at a Time."