Factors increasing the need for hospitalization include:

Age greater than 65
Underlying chronic illnesses
Respiratory rate greater than 30 per minute
Systolic blood pressure less than 90 mmHg
Heart rate greater than 125 per minute
Temperature below 35 or over 40 °C
Confusion
Evidence of infection outside the lungLaboratory results indicating hospitalization include:

Arterial oxygen tension less than 60 mm Hg
Carbon dioxide over 50 mmHg or pH under 7.35 while breathing room air
Hematocrit under 30 percent
Creatinine over 1.2 mg/dl or blood urea nitrogen over 20 mg/dl
White-blood-cell count under 4 × 10^9/L or over 30 × 10^9/L
Neutrophil count under 1 x 10^9/LX-ray findings indicating hospitalization include:

Involvement of more than one lobe of the lung
Presence of a cavity
Pleural effusion

Prognosis
The CAP outpatient mortality rate is less than one percent, with fever typically responding within the first two days of therapy, and other symptoms abating in the first week. However, X-rays may remain abnormal for at least a month. Hospitalized patients have an average mortality rate of 12 percent, with the rate rising to 40 percent for patients with bloodstream infections or those who require intensive care. Factors increasing mortality are identical to those indicating hospitalization. When CAP does not respond to treatment, this may indicate a previously unknown health problem, a treatment complication, inappropriate antibiotics for the causative organism, a previously unsuspected microorganism (such as tuberculosis) or a condition mimicking CAP (such as granuloma with polyangiitis). Additional tests include X-ray computed tomography, bronchoscopy or lung biopsy. Epidemiology
CAP is common worldwide, and is a major cause of death in all age groups.
Community-acquired pneumonia (CAP) refers to pneumonia (any of several lung diseases) contracted by a person outside of the healthcare system. In contrast, hospital-acquired pneumonia (HAP) is seen in patients who have recently visited a hospital or who live in long-term care facilities. CAP is common, affecting people of all ages, and its symptoms occur as a result of oxygen-absorbing areas of the lung (alveoli) filling with fluid. This inhibits lung function, causing dyspnea, fever, chest pains and cough. CAP, the most common type of pneumonia, is a leading cause of illness and death worldwide. Its causes include bacteria, viruses, fungi and parasites. CAP is diagnosed by assessing symptoms, performing a physical examination, by x-ray or by sputum examination. Patients with CAP sometimes require hospitalization, and it is treated primarily with antibiotics, antipyretics and cough medicine. Some forms of CAP can be prevented by vaccination and by abstaining from tobacco products. Signs and symptoms
Common symptoms
Coughing which produces greenish or yellow sputum
A high fever, accompanied by sweating, chills and shivering
Sharp, stabbing chest pains
Rapid, shallow, often painful breathing

Less-common symptoms
Coughing up blood (hemoptysis)
Headaches, including migraines
Loss of appetite
Excessive fatigue
Bluish skin (cyanosis)
Nausea
Vomiting
Diarrhea
Joint pain (arthralgia)
Muscle aches (myalgia)
Rapid heartbeat
Dizziness or lightheadedness

In the elderly
New or worsening confusion
Hypothermia
Poor coordination, which may lead to falls

In infants
Unusual sleepiness
Yellowing of the skin (jaundice)
Difficulty feeding

Complications
Major complications of CAP include:

Sepsis - A life-threatening reaction to infection. A common cause of sepsis is bacterial pneumonia, frequently the result of infection with streptococcus pneumoniae. Patients with sepsis require intensive care with blood pressure monitoring and support against hypotension.