ICD-10-CM Code R50.9

Fever, unspecified

Version 2020 Billable Code No Valid Principal Dx

Valid for Submission

R50.9 is a billable code used to specify a medical diagnosis of fever, unspecified. The code is valid for the year 2020 for the submission of HIPAA-covered transactions. The ICD-10-CM code R50.9 might also be used to specify conditions or terms like abnormal gamma globulin level, acute rise of fever, aseptic fever, biphasic fever, body temperature above reference range, central fever, etc

According to ICD-10-CM guidelines this code should not to be used as a principal diagnosis code when a related definitive diagnosis has been established.

Short Description:Fever, unspecified
Long Description:Fever, unspecified

Tabular List of Diseases and Injuries

The Tabular List of Diseases and Injuries is a list of ICD-10 codes, organized "head to toe" into chapters and sections with guidance for inclusions, exclusions, descriptions and more. The following references are applicable to the code R50.9:

Inclusion Terms

Inclusion Terms
These terms are the conditions for which that code is to be used. The terms may be synonyms of the code title, or, in the case of "other specified" codes, the terms are a list of the various conditions assigned to that code. The inclusion terms are not necessarily exhaustive. Additional terms found only in the Alphabetic Index may also be assigned to a code.
  • Fever NOS
  • Fever of unknown origin FUO
  • Fever with chills
  • Fever with rigors
  • Hyperpyrexia NOS
  • Persistent fever
  • Pyrexia NOS

Index to Diseases and Injuries

The Index to Diseases and Injuries is an alphabetical listing of medical terms, with each term mapped to one or more ICD-10 code(s). The following references for the code R50.9 are found in the index:


The following clinical terms are approximate synonyms or lay terms that might be used to identify the correct diagnosis code:

  • Abnormal gamma globulin level
  • Acute rise of fever
  • Aseptic fever
  • Biphasic fever
  • Body temperature above reference range
  • Central fever
  • Chill
  • Chronic fever
  • Continuous fever
  • Cough with fever
  • Desquamation of skin following febrile illness
  • Disorder characterized by fever
  • Endocrine hyperthermia
  • Factitious fever
  • Falling phase of fever
  • Febrile leukopenia
  • Feeling feverish
  • Feels hot/feverish
  • Fever
  • Fever defervescence
  • Fever greater than 100.4 Fahrenheit
  • Fever symptoms
  • Fever with chills
  • Fever with infection
  • Fever, diurnal variation
  • Feverish cold
  • Finding of temperature of skin
  • Gradual fall of fever
  • Gradual rise of fever
  • Humoral immune defect
  • Hyperimmunoglobulin D with periodic fever
  • Hyperpyrexia
  • Hyperpyrexia
  • Hyperthermia-hyperphagia-hypothyroidism syndrome
  • Hysterical fever
  • Increased skin temperature
  • Intermittent fever
  • Irregular fever
  • Low grade pyrexia
  • Malignant hyperthermia
  • Malignant hyperthermia with arthrogryposis and torticollis syndrome
  • Myoclonus associated with fever
  • Neurogenic hyperthermia
  • O/E - character of fever
  • O/E - fever
  • O/E - fever - acute rise
  • O/E - fever - continuous
  • O/E - fever - fast fall-crisis
  • O/E - fever - general
  • O/E - fever - gradual rise
  • O/E - fever - intermittent
  • O/E - fever - irregular
  • O/E - fever - remittent
  • O/E - fever-gradual fall-lysis
  • O/E - hyperpyrexia
  • O/E - hyperpyrexia - greater than 40.5 degrees Celsius
  • O/E - level of fever
  • O/E - pyrexia of unknown origin
  • O/E - staircase fever
  • O/E - temperature elevated
  • Pel Ebstein fever
  • Plateau phase of fever
  • Prolonged fever
  • Pyrexia of unknown origin
  • Pyrexia of unknown origin co-occurrent with human immunodeficiency virus infection
  • Rapid fall of fever
  • Remittent fever
  • Reversed diurnal fever
  • Rising phase of fever
  • Selective immunoglobulin dysfunction
  • Severe fever with thrombocytopenia syndrome virus
  • Shivering or rigors
  • Skin peeling disorder
  • Slightly remittent fever
  • Spiking fever
  • Staircase fever
  • Sweating fever
  • Swinging fever
  • Temperature symptoms
  • Temperature symptoms
  • Viral fever
  • Viral fever

Clinical Information

  • ZIKA VIRUS INFECTION-. a viral disease transmitted by the bite of aedes mosquitoes infected with zika virus. its mild dengue like symptoms include fever rash headaches and arthralgia. the viral infection during pregnancy in rare cases is a cause of congenital brain abnormalities including microcephaly and may also lead to guillain barre syndrome.
  • SPOTTED FEVER GROUP RICKETTSIOSIS-. a group of arthropod borne diseases caused by spotted fever bio group members of rickettsia. they are characterized by fever headache and petechial spotted rash.
  • ADENOVIRUS INFECTIONS HUMAN-. respiratory and conjunctival infections caused by 33 identified serotypes of human adenoviruses.
  • BARTONELLA INFECTIONS-. infections by the genus bartonella. bartonella bacilliformis can cause acute febrile anemia designated oroya fever and a benign skin eruption called verruga peruana. bartonella quintana causes trench fever while bartonella henselae is the etiologic agent of bacillary angiomatosis angiomatosis bacillary and is also one of the causes of cat scratch disease.
  • BLACKWATER FEVER-. a complication of malaria falciparum characterized by the passage of dark red to black urine.
  • BOUTONNEUSE FEVER-. a febrile disease of the mediterranean area the crimea africa and india caused by infection with rickettsia conorii.
  • BRUCELLOSIS-. infection caused by bacteria of the genus brucella mainly involving the mononuclear phagocyte system. this condition is characterized by fever weakness malaise and weight loss.
  • CAT SCRATCH DISEASE-. a self limiting bacterial infection of the regional lymph nodes caused by afipia felis a gram negative bacterium recently identified by the centers for disease control and prevention and by bartonella henselae. it usually arises one or more weeks following a feline scratch with raised inflammatory nodules at the site of the scratch being the primary symptom.
  • COLORADO TICK FEVER-. a febrile illness characterized by chills aches vomiting leukopenia and sometimes encephalitis. it is caused by the colorado tick fever virus a reovirus transmitted by the tick dermacentor andersoni.
  • SEIZURES FEBRILE-. seizures that occur during a febrile episode. it is a common condition affecting 2 5% of children aged 3 months to five years. an autosomal dominant pattern of inheritance has been identified in some families. the majority are simple febrile seizures generally defined as generalized onset single seizures with a duration of less than 30 minutes. complex febrile seizures are characterized by focal onset duration greater than 30 minutes and/or more than one seizure in a 24 hour period. the likelihood of developing epilepsy i.e. a nonfebrile seizure disorder following simple febrile seizures is low. complex febrile seizures are associated with a moderately increased incidence of epilepsy. from menkes textbook of child neurology 5th ed p784
  • HEPATITIS D-. inflammation of the liver in humans caused by hepatitis delta virus a defective rna virus that can only infect hepatitis b patients. for its viral coating hepatitis delta virus requires the hepatitis b surface antigens produced by these patients. hepatitis d can occur either concomitantly with coinfection or subsequent to superinfection hepatitis b infection. similar to hepatitis b it is primarily transmitted by parenteral exposure such as transfusion of contaminated blood or blood products but can also be transmitted via sexual or intimate personal contact.
  • DENGUE-. an acute febrile disease transmitted by the bite of aedes mosquitoes infected with dengue virus. it is self limiting and characterized by fever myalgia headache and rash. severe dengue is a more virulent form of dengue.
  • DENGUE VIRUS-. a species of the genus flavivirus which causes an acute febrile and sometimes hemorrhagic disease in man. dengue is mosquito borne and four serotypes are known.
  • EPHEMERAL FEVER-. an ephemerovirus infection of cattle caused by bovine ephemeral fever virus ephemeral fever virus bovine. it is characterized by respiratory symptoms increased oropharyngeal secretions and lacrimation joint pains tremor and stiffness.
  • EQUINE INFECTIOUS ANEMIA-. viral disease of horses caused by the equine infectious anemia virus eiav; infectious anemia virus equine. it is characterized by intermittent fever weakness and anemia. chronic infection consists of acute episodes with remissions.
  • FELINE PANLEUKOPENIA-. a highly contagious dna virus infection of the cat family characterized by fever enteritis and bone marrow changes. it is also called feline ataxia feline agranulocytosis feline infectious enteritis cat fever cat plague and show fever. it is caused by feline panleukopenia virus or the closely related mink enteritis virus or canine parvovirus.
  • FEVER-. an abnormal elevation of body temperature usually as a result of a pathologic process.
  • FEVER OF UNKNOWN ORIGIN-. fever in which the etiology cannot be ascertained.
  • RHINITIS ALLERGIC SEASONAL-. allergic rhinitis that occurs at the same time every year. it is characterized by acute conjunctivitis with lacrimation and itching and regarded as an allergic condition triggered by specific allergens.
  • HEMORRHAGIC FEVER AMERICAN-. diseases caused by american hemorrhagic fever viruses arenaviruses new world.
  • HEMORRHAGIC FEVER CRIMEAN-. a severe often fatal disease in humans caused by the crimean congo hemorrhagic fever virus hemorrhagic fever virus crimean congo.
  • HEMORRHAGIC FEVER OMSK-. infection with the omsk hemorrhagic fever virus a flavivirus.
  • HEMORRHAGIC FEVERS VIRAL-. a group of viral diseases of diverse etiology but having many similar clinical characteristics; increased capillary permeability leukopenia and thrombocytopenia are common to all. hemorrhagic fevers are characterized by sudden onset fever headache generalized myalgia backache conjunctivitis and severe prostration followed by various hemorrhagic symptoms. hemorrhagic fever with kidney involvement is hemorrhagic fever with renal syndrome.
  • HERPES LABIALIS-. herpes simplex caused by type 1 virus primarily spread by oral secretions and usually occurring as a concomitant of fever. it may also develop in the absence of fever or prior illness. it commonly involves the facial region especially the lips and the nares. dorland 27th ed.
  • HYPERTHERMIA INDUCED-. abnormally high temperature intentionally induced in living things regionally or whole body. it is most often induced by radiation heat waves infra red ultrasound or drugs.
  • INFECTIOUS MONONUCLEOSIS-. a common acute infection usually caused by the epstein barr virus herpesvirus 4 human. there is an increase in mononuclear white blood cells and other atypical lymphocytes generalized lymphadenopathy splenomegaly and occasionally hepatomegaly with hepatitis.
  • LASSA FEVER-. an acute febrile human disease caused by the lassa virus.
  • LEGIONNAIRES' DISEASE-. an acute sometimes fatal pneumonia like bacterial infection characterized by high fever malaise muscle aches respiratory disorders and headache. it is named for an outbreak at the 1976 philadelphia convention of the american legion.
  • LEISHMANIASIS VISCERAL-. a chronic disease caused by leishmania donovani and transmitted by the bite of several sandflies of the genera phlebotomus and lutzomyia. it is commonly characterized by fever chills vomiting anemia hepatosplenomegaly leukopenia hypergammaglobulinemia emaciation and an earth gray color of the skin. the disease is classified into three main types according to geographic distribution: indian mediterranean or infantile and african.
  • LEPTOSPIROSIS-. infections with bacteria of the genus leptospira.
  • MALARIA-. a protozoan disease caused in humans by four species of the plasmodium genus: plasmodium falciparum; plasmodium vivax; plasmodium ovale; and plasmodium malariae; and transmitted by the bite of an infected female mosquito of the genus anopheles. malaria is endemic in parts of asia africa central and south america oceania and certain caribbean islands. it is characterized by extreme exhaustion associated with paroxysms of high fever; sweating; shaking chills; and anemia. malaria in animals is caused by other species of plasmodia.
  • MALIGNANT CATARRH-. a herpesvirus infection of cattle characterized by catarrhal inflammation of the upper respiratory and alimentary epithelia keratoconjunctivitis encephalitis and lymph node enlargement. syn: bovine epitheliosis snotsiekte.
  • MARBURG VIRUS DISEASE-. an rna virus infection of rhesus vervet and squirrel monkeys transmissible to man.
  • PARATYPHOID FEVER-. a prolonged febrile illness commonly caused by several paratyphi serotypes of salmonella enterica. it is similar to typhoid fever but less severe.
  • PARTURIENT PARESIS-. a disease of pregnant and lactating cows and ewes leading to generalized paresis and death. the disease which is characterized by hypocalcemia occurs at or shortly after parturition in cows and within weeks before or after parturition in ewes.
  • PNEUMONIA ATYPICAL INTERSTITIAL OF CATTLE-. a cattle disease of uncertain cause probably an allergic reaction.
  • Q FEVER-. an acute infectious disease caused by coxiella burnetii. it is characterized by a sudden onset of fever; headache; malaise; and weakness. in humans it is commonly contracted by inhalation of infected dusts derived from infected domestic animals animals domestic.
  • RAT BITE FEVER-. a syndrome characterized by recurring fever rash and arthralgias occurring days to weeks after a rat bite. the causative agents are either streptobacillus moniliformis or spirillum minus.
  • RELAPSING FEVER-. an acute infection characterized by recurrent episodes of pyrexia alternating with asymptomatic intervals of apparent recovery. this condition is caused by spirochetes of the genus borrelia. it is transmitted by the bites of either the body louse pediculus humanus corporis for which humans are the reservoir or by soft ticks of the genus ornithodoros for which rodents and other animals are the principal reservoirs.
  • RHEUMATIC FEVER-. a febrile disease occurring as a delayed sequela of infections with streptococcus pyogenes. it is characterized by multiple focal inflammatory lesions of the connective tissue structures such as the heart blood vessels and joints polyarthritis and brain and by the presence of aschoff bodies in the myocardium and skin.
  • RIFT VALLEY FEVER-. an acute infection caused by the rift valley fever virus an rna arthropod borne virus affecting domestic animals and humans. in animals symptoms include hepatitis; abortion abortion veterinary; and death. in humans symptoms range from those of a flu like disease to hemorrhagic fever encephalitis or blindness.
  • ROCKY MOUNTAIN SPOTTED FEVER-. an acute febrile illness caused by rickettsia rickettsii. it is transmitted to humans by bites of infected ticks and occurs only in north and south america. characteristics include a sudden onset with headache and chills and fever lasting about two to three weeks. a cutaneous rash commonly appears on the extremities and trunk about the fourth day of illness.
  • SCARLET FEVER-. infection with group a streptococci that is characterized by tonsillitis and pharyngitis. an erythematous rash is commonly present.
  • SCHISTOSOMIASIS-. infection with flukes trematodes of the genus schistosoma. three species produce the most frequent clinical diseases: schistosoma haematobium endemic in africa and the middle east schistosoma mansoni in egypt northern and southern africa some west indies islands northern 2/3 of south america and schistosoma japonicum in japan china the philippines celebes thailand laos. s. mansoni is often seen in puerto ricans living in the united states.
  • SCRUB TYPHUS-. an acute infectious disease caused by orientia tsutsugamushi. it is limited to eastern and southeastern asia india northern australia and the adjacent islands. characteristics include the formation of a primary cutaneous lesion at the site of the bite of an infected mite fever lasting about two weeks and a maculopapular rash.
  • PASTEURELLOSIS PNEUMONIC-. bovine respiratory disease found in animals that have been shipped or exposed to cattle recently transported. the major agent responsible for the disease is mannheimia haemolytica and less commonly pasteurella multocida or haemophilus somnus. all three agents are normal inhabitants of the bovine nasal pharyngeal mucosa but not the lung. they are considered opportunistic pathogens following stress physiological and/or a viral infection. the resulting bacterial fibrinous bronchopneumonia is often fatal.
  • THEILERIASIS-. infection of cattle sheep or goats with protozoa of the genus theileria. this infection results in an acute or chronic febrile condition.
  • TRENCH FEVER-. an intermittent fever characterized by intervals of chills fever and splenomegaly each of which may last as long as 40 hours. it is caused by bartonella quintana and transmitted by the human louse.
  • TYPHOID FEVER-. an acute systemic febrile infection caused by salmonella typhi a serotype of salmonella enterica.
  • TYPHUS EPIDEMIC LOUSE BORNE-. the classic form of typhus caused by rickettsia prowazekii which is transmitted from man to man by the louse pediculus humanus corporis. this disease is characterized by the sudden onset of intense headache malaise and generalized myalgia followed by the formation of a macular skin eruption and vascular and neurologic disturbances.
  • UVEOPAROTID FEVER-. a manifestation of sarcoidosis marked by chronic inflammation of the parotid gland and the uvea.
  • YELLOW FEVER-. an acute infectious disease primarily of the tropics caused by a virus and transmitted to man by mosquitoes of the genera aedes and haemagogus. the severe form is characterized by fever hemolytic jaundice and renal damage.
  • SEVERE DENGUE-. a virulent form of dengue characterized by thrombocytopenia and an increase in vascular permeability grades i and ii and distinguished by a positive pain test e.g. tourniquet pain test. when accompanied by shock grades iii and iv it is called dengue shock syndrome.
  • TANACETUM PARTHENIUM-. an aromatic perennial plant species that has been used to treat migraines arthritis and as a febrifuge. it contains tannins volatile oils oils essential and sesquiterpene lactones especially parthenolide.
  • YELLOW FEVER VACCINE-. vaccine used to prevent yellow fever. it consists of a live attenuated 17d strain of the yellow fever virus.
  • ORNITHODOROS-. a genus of softbacked ticks in the family argasidae serving as the vector of borrelia causing relapsing fever and of the african swine fever virus.
  • HEREDITARY AUTOINFLAMMATORY DISEASES-. hereditary inflammation conditions characterized by recurrent episodes of systemic inflammation. common symptoms include recurrent fever rash arthritis fatigue and secondary amyloidosis. hereditary autoinflammatory diseases are associated with mutations in genes involved in regulation of normal inflammatory process and are not caused by autoantibodies or antigen specific t lymphocytes.
  • CHIKUNGUNYA FEVER-. an acute infection caused by a mosquito borne alphavirus chikungunya virus characterized by rash; fever; joint pains; conjunctivitis; meningoencephalitis; lymphopenia; and thrombocytopenia.

Convert R50.9 to ICD-9

  • 780.60 - Fever NOS (Approximate Flag)

Code Classification

  • Symptoms, signs and abnormal clinical and laboratory findings, not elsewhere classified (R00–R99)
    • General symptoms and signs (R50-R69)
      • Fever of other and unknown origin (R50)

Code History

  • FY 2016 - New Code, effective from 10/1/2015 through 9/30/2016
    (First year ICD-10-CM implemented into the HIPAA code set)
  • FY 2017 - No Change, effective from 10/1/2016 through 9/30/2017
  • FY 2018 - No Change, effective from 10/1/2017 through 9/30/2018
  • FY 2019 - No Change, effective from 10/1/2018 through 9/30/2019
  • FY 2020 - No Change, effective from 10/1/2019 through 9/30/2020

Information for Patients


A fever is a body temperature that is higher than normal. A normal temperature can vary from person to person, but it is usually around 98.6 F. A fever is not a disease. It is usually a sign that your body is trying to fight an illness or infection.

Infections cause most fevers. You get a fever because your body is trying to kill the virus or bacteria that caused the infection. Most of those bacteria and viruses do well when your body is at your normal temperature. But if you have a fever, it is harder for them to survive. Fever also activates your body's immune system.

Other causes of fevers include

  • Medicines, including some antibiotics, blood pressure medicines, and anti-seizure medicines
  • Heat illness
  • Cancers
  • Autoimmune diseases
  • Some childhood immunizations

Treatment depends on the cause of your fever. If the fever is very high, your health care provider may recommend taking an over-the-counter medicine such as acetaminophen or ibuprofen. Adults can also take aspirin, but children with fevers should not take aspirin. It is also important to drink enough liquids, to prevent dehydration.

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