Ask a Doctor
I’ve had what feels like influenza for more than three days now – fever, weakness, fatigue – and it doesn’t seem to be getting better. This morning I noticed blood in the phlegm I coughed up. Should I see a doctor? When should you go to the hospital if you have the flu?
You should contact your doctor or seek care in a hospital's emergency department for the following symptoms, which may be a sign of complications:
- Dehydration and unable to drink fluids
- Bloody or brown sputum (saliva mixed with mucus and coughed up)
- Difficulty breathing
- Turning blue (a sign of poor oxygenation)
- Worsening fever
- Return of fever, cough, and other symptoms in the second week after the onset of the flu or worsening after symptoms have begun to improve
These symptoms and signs may signify a more severe and complicated attack of flu (most importantly, the development of pneumonia). Pneumonia is an infection of the lungs, and it may be caused by the flu virus itself or by a bacterial infection that may occur when the person is weakened during a flu attack.
Flu symptoms start to go away after two to five days. Fever may last for up to five days, while other symptoms, including weakness and fatigue, may persist for several weeks. The very young, the very old, and those in the high-risk groups are at risk for complications requiring hospitalization. Some people may die from the flu.
Quite a few groups of people are at high risk for developing complications of the flu (of course, anyone can develop serious complications and may be unaware of being at high risk). Groups at high risk include the following:
- Those with chronic diseases of the heart, lungs, liver, blood, or kidneys (any condition that affects a major organ system)
- Pregnant women
- People with obesity (body mass index or BMI over 40)
- People with diabetes
- People with disorders of the brain, spinal cord, peripheral nerves, or muscles (examples include cerebral palsy, seizures, intellectual disability, stroke, and spinal cord injury)
- People with weak immune systems due to disease or medication (such as people with HIV infection, or who are on chronic steroids or tumor necrosis alpha inhibitor drugs)
- People with cancer, including cancer survivors
- People with disorders of metabolism or mitochondria
- Residents of nursing homes and other facilities
- People older than 65 years of age
- People on long-term aspirin therapy
- People who provide care to those at high risk for complications of flu, such as home caregivers, preschool workers, or health care workers
People in a high-risk group should receive the flu vaccine and pneumococcal vaccines before the start of flu season. Pneumococcus is one of the most common causes of bacterial pneumonia that is preventable by vaccine. They should be especially aware of when to see a doctor or go to the hospital. People at high risk may benefit from early treatment with antiviral drugs that combat the influenza virus.
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Mandell, Douglas, John E. Bennett, and Raphael Dolin. Mandell, Douglas, and Bennett's Principles and Practice of Infectious Diseases. Seventh Edition. "Influenza Viruses, Including Avian Influenza and Swine Influenza." Philadelphia: Churchill Livingstone Elsevier, 2010.
Switzerland. World Health Organization. "Influenza." <http://www.who.int/topics/influenza/en/>.
United States. Centers for Disease Control and Prevention. "Seasonal Influenza (Flu)." <http://CDC.gov/flu>.
United States. Department of Health & Human Services. "Seasonal Flu."