ICD-10 Code for Fever

The default ICD-10-CM 2027 code for fever (inanition) (of unknown origin) (persistent) (with chills) (with rigor) is R50.9 – Fever, unspecified. More specific codes depend on the details documented, as listed in the official index (130 codes, 126 billable).

Main code: R50.9 – Fever, unspecified
Billable: Yes

Index entries for Fever

abortus – A23.1
Aden (dengue) – A90
African tick bite – A77.8
African tick-borne – A68.1
American
- mountain (tick) – A93.2
- spotted – A77.0
aphthous – B08.8
arbovirus, arboviral – A94
- hemorrhagic – A94
- specified NEC – A93.8
Argentinian hemorrhagic – A96.0
Assam – B55.0
Australian Q – A78
Bangkok hemorrhagic – A91
Barmah forest – A92.8
Bartonella – A44.0
bilious, hemoglobinuric – B50.8
blackwater – B50.8
blister – B00.1
Bolivian hemorrhagic – A96.1
Bonvale dam – T73.3 (header)
boutonneuse – A77.1
brain – see Encephalitis
Brazilian purpuric – A48.4
breakbone – A90
Bullis – A77.0
Bunyamwera – A92.8
Burdwan – B55.0
Bwamba – A92.8
Cameroon – see Malaria
Canton – A75.9
catarrhal (acute) – J00
- chronic – J31.0
cat-scratch – A28.1
Central Asian hemorrhagic – A98.0
cerebral – see Encephalitis
cerebrospinal meningococcal – A39.0
Chagres – B50.9
Chandipura – A92.8
Changuinola – A93.1
Charcot's (biliary) (hepatic) (intermittent) – see Calculus, bile duct
Chikungunya (viral) (hemorrhagic) – A92.0
Chitral – A93.1
Colombo – see Fever, paratyphoid
Colorado tick (virus) – A93.2
congestive (remittent) – see Malaria
Congo virus – A98.0
continued malarial – B50.9
Corsican – see Malaria
Crimean-Congo hemorrhagic – A98.0
Cyprus – see Brucellosis
dandy – A90
deer fly – see Tularemia
dengue (virus) – A90
- hemorrhagic – A91
- sandfly – A93.1
desert – B38.0
drug induced – R50.2
due to
- conditions classified elsewhere – R50.81
- heat – T67.01 (header)
enteric – A01.00
enteroviral exanthematous (Boston exanthem) – A88.0
ephemeral (of unknown origin) – R50.9
epidemic hemorrhagic – A98.5
erysipelatous – see Erysipelas
estivo-autumnal (malarial) – B50.9
famine – A75.0
five day – A79.0
following delivery – O86.4
Fort Bragg – A27.89
gastroenteric – A01.00
gastromalarial – see Malaria
Gibraltar – see Brucellosis
glandular – see Mononucleosis, infectious
Guama (viral) – A92.8
Haverhill – A25.1
hay (allergic) – J30.1
- with asthma (bronchial) – J45.909
  - with
    - exacerbation (acute) – J45.901
    - status asthmaticus – J45.902
- due to
  - allergen other than pollen – J30.89
  - pollen, any plant or tree – J30.1
heat (effects) – T67.01 (header)
hematuric, bilious – B50.8
hemoglobinuric (malarial) (bilious) – B50.8
hemorrhagic (arthropod-borne) – A94
- with renal syndrome – A98.5
- arenaviral – A96.9
  - specified NEC – A96.8
- Argentinian – A96.0
- Bangkok – A91
- Bolivian – A96.1
- Central Asian – A98.0
- Chikungunya – A92.0
- Crimean-Congo – A98.0
- dengue (virus) – A91
- epidemic – A98.5
- Junin (virus) – A96.0
- Korean – A98.5
- Kyasanur forest – A98.2
- Machupo (virus) – A96.1
- mite-borne – A93.8
- mosquito-borne – A92.8
- Omsk – A98.1
- Philippine – A91
- Russian – A98.5
- Singapore – A91
- Southeast Asia – A91
- Thailand – A91
- tick-borne NEC – A93.8
- viral – A99
  - specified NEC – A98.8
hepatic – see Cholecystitis
herpetic – see Herpes
icterohemorrhagic – A27.0
Indiana – A93.8
infective – B99.9
- specified NEC – B99.8
intermittent (bilious) – see also Malaria
- of unknown origin – R50.9
- pernicious – B50.9
iodide – R50.2
Japanese river – A75.3
jungle – see also Malaria
- yellow – A95.0
Junin (virus) – A96.0
Katayama – B65.2
kedani – A75.3
Kenya (tick) – A77.1
Kew Garden – A79.1
Korean hemorrhagic – A98.5
Lassa – A96.2
Lone Star – A77.0
Machupo (virus) – A96.1
malaria, malarial – see Malaria
Malta – A23.9
Marseilles – A77.1
marsh – see Malaria
Mayaro (viral) – A92.8
Mediterranean – A23.9 – see also Brucellosis
- familial – M04.1
- tick – A77.1
meningeal – see Meningitis
Meuse – A79.0
Mexican – A75.2
mianeh – A68.1
miasmatic – see Malaria
mosquito-borne (viral) – A92.9
- hemorrhagic – A92.8
mountain – see also Brucellosis
- meaning Rocky Mountain spotted fever – A77.0
- tick (American) (Colorado) (viral) – A93.2
Mucambo (viral) – A92.8
mud – A27.9
Neapolitan – see Brucellosis
neutropenic – D70.9
newborn – P81.9
- environmental – P81.0
Nine-Mile – A78
non-exanthematous tick – A93.2
North Asian tick-borne – A77.2
Omsk hemorrhagic – A98.1
O'nyong-nyong (viral) – A92.1
Oropouche (viral) – A93.0
Oroya – A44.0
pacific coast tick – A77.8
paludal – see Malaria
Panama (malarial) – B50.9
Pappataci – A93.1
paratyphoid – A01.4
- A – A01.1
- B – A01.2
- C – A01.3
parrot – A70
periodic (Mediterranean) – M04.1
persistent (of unknown origin) – R50.9
petechial – A39.0
pharyngoconjunctival – B30.2
Philippine hemorrhagic – A91
phlebotomus – A93.1
Piry (virus) – A93.8
Pixuna (viral) – A92.8
Plasmodium ovale – B53.0
polioviral (nonparalytic) – A80.4
Pontiac – A48.2
postimmunization – R50.83
postoperative – R50.82
- due to infection – T81.40 (header)
posttransfusion – R50.84
postvaccination – R50.83
presenting with conditions classified elsewhere – R50.81
pretibial – A27.89
puerperal – O86.4
Q – A78
quadrilateral – A78
quartan (malaria) – B52.9
Queensland (coastal) (tick) – A77.3
quintan – A79.0
rabbit – see Tularemia
rat-bite – A25.9
- due to
  - Spirillum – A25.0
  - Streptobacillus moniliformis – A25.1
recurrent – see Fever, relapsing
relapsing (Borrelia) – A68.9
- Carter's (Asiatic) – A68.1
- Dutton's (West African) – A68.1
- Koch's – A68.9
- louse-borne – A68.0
- Novy's
  - louse-borne – A68.0
  - tick-borne – A68.1
- Obermeyer's (European) – A68.0
- tick-borne – A68.1
remittent (bilious) (congestive) (gastric) – see Malaria
rheumatic (active) (acute) (chronic) (subacute) – I00
- with central nervous system involvement – I02.9
- active with heart involvement – I01 (header) – see category
- inactive or quiescent with
  - cardiac hypertrophy – I09.89
  - carditis – I09.9
  - endocarditis – I09.1
    - aortic (valve) – I06.9
      - with mitral (valve) – I08.0
    - mitral (valve) – I05.9
      - with aortic (valve) – I08.0
    - pulmonary (valve) – I09.89
    - tricuspid (valve) – I07.8
  - heart disease NEC – I09.89
  - heart failure (congestive) (conditions in category I50.) – I09.81
  - left ventricular failure (conditions in I50.1-I50.4-) – I09.81
  - myocarditis, myocardial degeneration (conditions in I51.4) – I09.0
  - pancarditis – I09.9
  - pericarditis – I09.2
Rift Valley (viral) – A92.4
Rocky Mountain spotted – A77.0
rose – J30.1
Ross River – B33.1
Russian hemorrhagic – A98.5
San Joaquin (Valley) – B38.0
sandfly – A93.1
Sao Paulo – A77.0
scarlet – A38.9
seven day (leptospirosis) (autumnal) (Japanese) – A27.89
- dengue – A90
shin-bone – A79.0
Singapore hemorrhagic – A91
solar – A90
Songo – A98.5
sore – B00.1
South African tick-bite – A68.1
Southeast Asia hemorrhagic – A91
spinal – see Meningitis
spirillary – A25.0
splenic – see Anthrax
spotted – A77.9
- American – A77.0
- Brazilian – A77.0
- cerebrospinal meningitis – A39.0
- Colombian – A77.0
- due to Rickettsia
  - africae (African tick bite fever) – A77.8
  - australis – A77.3
  - conorii – A77.1
  - parkeri – A77.8
  - rickettsii – A77.0
  - sibirica – A77.2
  - specified type NEC – A77.8
- Ehrlichiosis – A77.40
  - due to
    - E. chaffeensis – A77.41
    - specified organism NEC – A77.49
- Rocky Mountain – A77.0
steroid – R50.2
streptobacillary – A25.1
subtertian – B50.9
Sumatran mite – A75.3
sun – A90
swamp – A27.9
swine – A02.8
sylvatic, yellow – A95.0
Tahyna – B33.8
tertian – see Malaria, tertian
Thailand hemorrhagic – A91
thermic – T67.01 (header)
three-day – A93.1
tick
- American mountain – A93.2
- Colorado – A93.2
- Kemerovo – A93.8
- Mediterranean – A77.1
- mountain – A93.2
- nonexanthematous – A93.2
- Quaranfil – A93.8
tick-bite NEC – A93.8
tick-borne (hemorrhagic) – A93.8
trench – A79.0
tsutsugamushi – A75.3
typhogastric – A01.00
typhoid (abortive) (hemorrhagic) (intermittent) (malignant) – A01.00
- complicated by
  - arthritis – A01.04
  - heart involvement – A01.02
  - meningitis – A01.01
  - osteomyelitis – A01.05
  - pneumonia – A01.03
  - specified NEC – A01.09
typhomalarial – see Malaria
typhus – see Typhus (fever)
undulant – see Brucellosis
unknown origin – R50.9
uveoparotid – D86.89
valley – B38.0
Venezuelan equine – A92.2
vesicular stomatitis – A93.8
viral hemorrhagic – see Fever, hemorrhagic, by type of virus
Volhynian – A79.0
Wesselsbron (viral) – A92.8
West
- African – B50.8
- Nile (viral) – A92.30
  - with
    - complications NEC – A92.39
    - cranial nerve disorders – A92.32
    - encephalitis – A92.31
    - encephalomyelitis – A92.31
    - neurologic manifestation NEC – A92.32
    - optic neuritis – A92.32
    - polyradiculitis – A92.32
Whitmore's – see Melioidosis
Wolhynian – A79.0
worm – B83.9
yellow – A95.9
- jungle – A95.0
- sylvatic – A95.0
- urban – A95.1
Zika virus – A92.5

How to choose the right code

Start with the main term, then pick the indented subterm that matches the documentation (type, cause, site, laterality, episode of care). Always confirm the code in the tabular list: follow its Excludes1/Excludes2, “code first” and “use additional code” notes, and add a 7th character where required.

Source: CDC/NCHS ICD-10-CM FY2027 alphabetic index.