What is the ICD‑10 code for a tick bite in adults?

Understanding ICD‑10 Codes

What are ICD‑10 Codes?

Purpose and Structure

The ICD‑10 classification assigns a specific code to a tick bite in adults to enable consistent recording, reimbursement, and statistical analysis. The code captures the clinical encounter, supports health‑system reporting, and facilitates research on vector‑borne diseases.

The code’s structure reflects the hierarchical design of ICD‑10:

Chapter XVIII (Certain infectious and parasitic diseases) – groups diseases caused by infectious agents.
Block B80‑B89 – covers infections and infestations caused by arthropods and other vectors.
Category B86 – designated for “Infection due to other arthropods.”
Subcategory B86.0 – denotes a “Tick bite.”

Each level narrows the classification from broad disease groups to the precise clinical manifestation, ensuring that the encounter is documented with the appropriate degree of specificity.

Importance in Healthcare

Accurate classification of tick‑bite encounters in adult patients using the appropriate ICD‑10 identifier supports multiple clinical and administrative processes. The code aligns documentation with reimbursement systems, ensuring that services related to diagnosis, laboratory testing, and treatment are billed correctly and audited efficiently.

Facilitates epidemiological tracking of tick‑borne disease incidence across regions.
Enables health‑information systems to generate alerts for emerging vector‑borne threats.
Provides a standardized reference for research studies evaluating preventive measures and therapeutic outcomes.
Assists insurance providers in validating claims and managing resource allocation.

Consistent use of the specific code improves patient records, allowing clinicians to retrieve prior exposure histories quickly and to apply evidence‑based guidelines for prophylaxis or treatment. Aggregated data derived from coded encounters inform public‑health interventions, such as targeted education campaigns and vector‑control programs, ultimately reducing disease burden and optimizing care delivery.

Specific ICD‑10 Codes for Tick Bites

General Codes for Tick Bites

Unspecified Tick Bite

The ICD‑10 classification assigns the code A68.0 to an unspecified bite or infestation caused by a tick. This code is used when the clinical documentation indicates a tick bite without further specification of the pathogen transmitted or the presence of disease sequelae.

When coding an adult patient with a tick bite of unspecified nature, follow these points:

Record A68.0 as the principal diagnosis if the encounter is for the bite itself.
Include any associated symptoms (e.g., erythema, pain) with appropriate secondary codes if they are documented.
Do not use Z‑codes for exposure unless the encounter is solely for preventive counseling without an actual bite.
Verify that the documentation confirms the bite occurred in an adult; age‑specific modifiers are not required for this code.

Accurate use of A68.0 ensures consistent reporting, facilitates epidemiological tracking of arthropod‑related injuries, and supports appropriate reimbursement.

Initial Encounter versus Subsequent Encounter

The ICD‑10 classification assigns the external‑cause code W57.0 for a tick bite. Because this code belongs to Chapter 20 (Injury, poisoning and certain other consequences of external causes), a seventh character is required to indicate the type of encounter.

Initial encounter – code W57.0XA. Use when the patient presents for the first assessment of the bite, including wound examination, laboratory testing, or initiation of prophylactic treatment.
Subsequent encounter – code W57.0XD. Use for follow‑up visits after the initial assessment, such as monitoring for signs of infection, adjusting therapy, or documenting resolution of the wound.

If the visit concerns only exposure without an actual bite or focuses on preventive counseling, the alternative code Z20.6 (Contact with and suspected exposure to other arthropods) may be appropriate, but it does not employ a seventh‑character modifier.

Codes for Tick Bites with Complications

Infected Tick Bite

The ICD‑10 classification assigns the code W75.0 to a tick bite. When the bite becomes infected, the primary code remains W75.0, and an additional code is required to capture the infection. The secondary code reflects the specific type of infection, such as cellulitis (L03.9), abscess (L02.9), or a bacterial infection of the skin and subcutaneous tissue (L08.9).

Clinical documentation must include:

Confirmation of a tick bite as the initiating event.
Evidence of infection (e.g., erythema, swelling, purulence, fever).
Identification of the infectious process (cellulitis, abscess, lymphangitis, etc.).

Coding guidelines:

Record W75.0 for the tick bite.
Add the appropriate infection code from Chapter L (Diseases of the skin and subcutaneous tissue).
If the infection is caused by a specific pathogen, append the corresponding bacterial code (e.g., A48.1 for rickettsial infection).

Accurate coding ensures proper reimbursement and facilitates epidemiological tracking of tick‑borne infections.

Tick-borne Diseases Resulting from a Bite

The ICD‑10 classification assigns the code W73.9 for an adult who has been bitten by a tick; the entry reads “Contact with other arthropods, unspecified,” and is used for tick‑related injuries when no more specific code exists.

Tick bites transmit a limited set of pathogens. The most frequently encountered diseases include:

Lyme disease – infection with Borrelia burgdorferi; early signs are erythema migrans and flu‑like symptoms, progressing to arthritis, neurologic involvement, or carditis if untreated.
Anaplasmosis – caused by Anaplasma phagocytophilum; presents with fever, leukopenia, thrombocytopenia, and elevated liver enzymes.
Ehrlichiosis – infection with Ehrlichia chaffeensis or related species; similar to anaplasmosis but may involve more severe cytopenias.
Babesiosis – caused by Babesia microti; characterized by hemolytic anemia, hemoglobinuria, and possible organ dysfunction.
Tick‑borne relapsing fever – infection with Borrelia spp.; marked by recurrent febrile episodes and possible neurologic complications.
Rocky Mountain spotted fever – caused by Rickettsia rickettsii; presents with fever, headache, and a characteristic rash that may become petechial.

Recognition of the appropriate ICD‑10 code and awareness of these potential infections enable accurate documentation, timely treatment, and reliable epidemiologic tracking.

Lyme Disease

The ICD‑10 classification assigns the code W57.0 to a tick bite encountered in an adult patient. This code covers direct contact with, or suspected exposure to, ticks and is used for billing and epidemiological reporting.

Lyme disease, caused by the spirochete Borrelia burgdorferi, is the most common infection transmitted by tick bites in temperate regions. The pathogen is introduced during the feeding phase of Ixodes ticks, typically after 36–48 hours of attachment.

Key clinical features:

Early localized stage: erythema migrans rash, flu‑like symptoms, headache.
Early disseminated stage: multiple rashes, cardiac conduction abnormalities, neurological signs such as facial palsy.
Late disseminated stage: arthritis, chronic neuropathy, encephalopathy.

Diagnosis relies on a two‑tier serologic algorithm: an initial enzyme‑linked immunosorbent assay (ELISA) followed by a confirmatory Western blot. Polymerase chain reaction (PCR) testing is reserved for cerebrospinal fluid or synovial fluid when serology is inconclusive.

Standard treatment consists of doxycycline for 14–21 days in uncomplicated cases; intravenous ceftriaxone is indicated for neuroborreliosis or severe cardiac involvement. Prompt therapy reduces the risk of progression to chronic manifestations.

Prevention strategies include regular tick checks, use of repellents containing DEET or permethrin, and prompt removal of attached ticks using fine‑tipped tweezers. Early identification of tick exposure, documented with code W57.0, facilitates timely clinical assessment for potential Lyme disease.

Rocky Mountain Spotted Fever

The ICD‑10 identifier assigned to a tick bite in an adult patient is W73.0 (Tick bite). This code is used in medical records to document exposure to a tick, which is the primary vector for Rocky Mountain Spotted Fever (RMSF).

Rocky Mountain Spotted Fever is a severe, acute illness caused by Rickettsia rickettsii. Key clinical features include:

Sudden fever and chills
Headache and muscle pain
Maculopapular rash that may become petechial, often beginning on wrists and ankles and spreading centrally
Potential complications such as encephalitis, renal failure, and vascular leakage

Diagnosis relies on a combination of epidemiologic exposure (tick bite), clinical presentation, and laboratory testing (serology, PCR). Early administration of doxycycline, typically 100 mg twice daily for adults, markedly reduces mortality.

Accurate coding of the tick bite (W73.0) facilitates epidemiological tracking of RMSF cases, ensures appropriate reimbursement, and supports timely public‑health interventions.

Anaplasmosis and Ehrlichiosis

The appropriate ICD‑10 classification for a tick bite in an adult is W86.0 (Contact with tick). This code records the exposure event and is used when a bite is documented without a confirmed infection.

When laboratory testing confirms a tick‑borne bacterial infection, the diagnosis is coded separately:

A79.3 – Anaplasmosis
A79.2 – Ehrlichiosis

Both conditions are transmitted by the same vector and share clinical features such as fever, headache, and leukopenia. Documentation should include the exposure code (W86.0) together with the disease‑specific code if the infection is established. This dual‑coding approach ensures accurate epidemiological tracking and appropriate reimbursement.

Factors Influencing Code Selection

Patient Demographics

Age (Adults vs. Children)

The ICD‑10 classification assigns the code B65.0 for a tick bite. This code is identical for patients of any age, including adults and children. When additional clinical details are required, the primary code can be supplemented with age‑specific codes from the Z‑section, such as Z00.0 for a routine health check of an adult or Z00.1 for a child’s health examination, to document the patient’s age group. If the bite results in a disease manifestation, the appropriate disease code (e.g., A68.0 for Lyme disease) is added alongside B65.0, regardless of age. Thus, the base ICD‑10 identifier for a tick bite does not change between adults and children; age‑related information is captured through auxiliary codes rather than a distinct primary code.

Location of Bite

Tick bites on adults most frequently occur in areas where the skin is thin, warm, and often concealed by clothing. Typical sites include the scalp, especially the hairline; the neck and behind the ears; the armpits; the groin; the waistline or belt area; and the flexor surfaces of the elbows and knees. Less common locations are the torso, back, and hands, where exposure is reduced by clothing.

When documenting the encounter for coding purposes, the anatomical site of the bite is recorded in the clinical note but does not alter the ICD‑10 classification. The appropriate code for a tick bite in an adult remains W57.0 (Bitten or stung by insect, unspecified). Accurate description of the bite location supports clinical assessment, particularly for evaluating the risk of localized infection or Lyme disease, while ensuring consistent coding across medical records.

Severity and Presentation of the Bite

Local Reactions

Tick bite in an adult is classified in ICD‑10 under code W75.0 (bite of other arthropod). The code applies whether the bite produces only a skin reaction or leads to further complications.

Local reactions represent the initial clinical presentation. Common manifestations include:

Erythema surrounding the attachment site, often circular and ranging from a few millimeters to several centimeters.
Papular or vesicular lesions that may develop within 24–48 hours.
Pruritus or burning sensation localized to the bite area.
Mild edema or induration of the surrounding tissue.
Small ulceration if the mandibles of the tick cause deeper skin breach.

These findings typically appear within hours to a few days after the bite. Documentation should note size, color, and any progression, as precise description supports accurate coding and facilitates monitoring for secondary infection or early signs of Lyme disease. Treatment focuses on removal of the tick, cleaning the site, and, when indicated, topical antiseptics or short‑course antibiotics for secondary bacterial infection. Recording the ICD‑10 code W75.0 together with detailed local reaction data ensures proper billing and epidemiological tracking.

Systemic Symptoms

The ICD‑10 classification for a tick bite in an adult patient is W73.0 (“Contact with ticks”). When documenting the encounter, the code should be paired with any systemic manifestations that develop, because these affect clinical management and reimbursement.

Systemic symptoms frequently associated with tick exposure include:

Fever or chills
Headache, often severe
Myalgia and arthralgia
Nausea, vomiting, or abdominal pain
Generalized fatigue
Rash, especially erythema migrans or other maculopapular lesions

If any of these signs are present, the coder must also assign the appropriate code from Chapter I (infectious and parasitic diseases) to reflect the underlying condition, such as A69.2 (Lyme disease) or A91 (Tick‑borne viral fever), in addition to W73.0. Documentation must specify the timing, severity, and duration of each systemic finding to justify secondary codes.

Accurate coding requires that the primary diagnosis be the tick bite (W73.0) when it is the chief complaint, with secondary codes capturing the systemic response. The combination ensures that the medical record reflects both the exposure and its clinical consequences, supporting precise data collection and appropriate reimbursement.

Clinical Documentation for Tick Bites

Essential Information for Medical Records

Date and Location of Bite

Accurate documentation of when and where a tick bite occurred is a prerequisite for assigning the appropriate ICD‑10 classification for an adult patient. The date of the incident establishes the temporal relationship to symptoms, distinguishes a new exposure from a follow‑up encounter, and determines whether the encounter is coded as an acute event or as a sequela. The anatomical site of the bite influences the code extension that specifies the affected body region, which is required for precise coding and reimbursement.

Key data elements to record:

Exact calendar date of the bite (day, month, year).
Time of day, if available, to support acute‑onset classification.
Precise anatomical location (e.g., scalp, forearm, lower leg), using standard body‑region terminology.
Contextual details such as outdoor setting, geographic region, and activity, which may be relevant for epidemiological tracking but are not mandatory for the code itself.

Collecting these details at the point of care ensures that the medical record contains the information needed for the correct ICD‑10 entry, reduces the risk of claim denial, and facilitates accurate public‑health surveillance of tick‑borne exposures.

Symptoms and Physical Examination Findings

Tick bites in adults often produce a distinct set of clinical manifestations that guide diagnosis and coding. The most frequent early sign is a localized erythematous area at the attachment site, which may evolve into an expanding annular rash with central clearing (erythema migrans). Patients may report pruritus, mild pain, or a sensation of warmth around the bite. Systemic complaints can appear within days to weeks and include low‑grade fever, chills, headache, malaise, myalgia, and arthralgia. Neurological involvement, although less common, may present as facial nerve palsy, meningitic symptoms, or peripheral neuropathy. In rare cases, cardiac manifestations such as atrioventricular block develop.

Physical examination typically reveals:

A circular or oval erythematous lesion, 5–10 cm in diameter, with a clear central area; the border is often raised and may be irregular.
The original tick attachment point, sometimes visible as a small punctum or scab.
Tender, enlarged regional lymph nodes, most often in the axillary or cervical chains.
Joint swelling or effusion, particularly in the knees or ankles, accompanied by limited range of motion.
Neurological deficits, including facial muscle weakness, decreased sensation, or abnormal reflexes.
Cardiovascular assessment may detect conduction abnormalities on ECG if cardiac involvement is suspected.

Recognition of these patterns enables accurate documentation and assignment of the appropriate ICD‑10 identifier for tick‑bite–related conditions in adult patients.

Diagnostic Tests Performed

When an adult presents after a tick attachment, clinicians assess the bite site and consider potential pathogen transmission. Diagnostic procedures focus on confirming infection, evaluating systemic involvement, and guiding therapy.

Physical inspection of the lesion, noting erythema, central punctum, or expanding rash.
Complete blood count with differential to identify leukocytosis, anemia, or thrombocytopenia.
Serologic testing for Borrelia burgdorferi: enzyme‑linked immunosorbent assay followed by confirmatory Western blot when early Lyme disease is suspected.
Polymerase chain reaction assays on blood or skin biopsy material for detection of Anaplasma, Ehrlichia, or other tick‑borne agents.
Urinalysis and renal function panel when symptoms suggest nephritis or systemic infection.
Imaging studies, such as joint ultrasound or MRI, if arthritic or neurologic manifestations develop.

These investigations support accurate coding of the encounter, typically recorded under ICD‑10 code W85.0 for contact with insects, not elsewhere classified.

Impact on Code Accuracy

Importance of Detailed Documentation

Accurate documentation is the foundation for assigning the correct ICD‑10 classification to a tick bite in an adult patient. Precise records enable coders to select the appropriate code, support billing integrity, and contribute reliable data for public‑health surveillance.

Key elements that must be captured in the clinical note include:

Date and time of the bite
Anatomical site of attachment
Species identification when available or description of the tick type
Presence of erythema, rash, or systemic symptoms
History of recent travel to endemic regions
Preventive measures taken (e.g., prophylactic antibiotics)

Each element should be recorded in a structured format, using standardized terminology and avoiding ambiguous language. Consistency across entries facilitates automated extraction and reduces the risk of miscoding.

Detailed documentation also clarifies whether the encounter represents a primary diagnosis of a tick bite or a secondary condition such as Lyme disease. When the bite itself is the focus, the coder selects the specific ICD‑10 code for the exposure; when disease manifestations are present, the appropriate infectious disease code is added. Clear separation of these diagnoses prevents claim denials and ensures appropriate reimbursement.

Finally, comprehensive records serve research and epidemiological purposes. Aggregated data on bite locations, tick species, and symptom patterns inform vector‑control strategies and guide resource allocation. Maintaining high‑quality documentation directly enhances patient care, financial accuracy, and public‑health outcomes.

Avoiding Underspecified Codes

When documenting a tick bite in an adult patient, the ICD‑10‑CM code B86.1 “Tick bite” should be selected rather than a generic arthropod bite code such as B86.9. The specific code conveys the exact etiology, supports accurate epidemiological tracking, and satisfies payer requirements for detailed diagnosis.

To prevent the use of underspecified codes, follow these steps:

Verify the exposure source; if the bite is confirmed to be from a tick, apply B86.1.
Include an appropriate external cause code (e.g., V71.0 “Contact with other and unspecified non‑communicable disease agents”) if required by the coding guidelines.
Add a seventh‑character extension for encounter type (A = initial, D = subsequent, S = sequela) when the system mandates it.
Review the patient’s record for any related conditions (e.g., Lyme disease, rickettsial infection) and code them separately if documented.

Consistently using the precise tick‑bite code eliminates ambiguity, improves data quality, and aligns with coding standards.

When to Seek Medical Attention for a Tick Bite

Signs and Symptoms Requiring Evaluation

Rash Development

A rash that appears after a tick attachment usually begins within 24–48 hours. The lesion is often erythematous, raised, and may be pruritic or painful. In many cases the rash expands outward, forming a target‑shaped or oval plaque that can reach several centimeters in diameter.

Typical characteristics include:

Central erythema with a clear or slightly raised border.
Peripheral spreading margin that may develop a vesicular or necrotic center.
Absence of systemic symptoms unless a secondary infection or pathogen, such as Borrelia burgdorferi, is involved.

For diagnostic coding, the appropriate ICD‑10 identifier for a tick‑bite‑related dermatitis in adults is B35.0. When the rash is accompanied by confirmed Lyme disease, the code A69.2 (Lyme disease) should be added in addition to B35.0. Documentation must specify the presence of a tick bite, the temporal relationship to rash onset, and any accompanying systemic manifestations to ensure accurate coding.

Flu-like Symptoms

The ICD‑10 classification assigns the code W75.0 for a tick bite, regardless of patient age. When a tick bite triggers systemic manifestations that resemble an influenza infection, clinicians must document both the external cause (W75.0) and the accompanying clinical picture.

Typical flu‑like manifestations after a tick bite include:

Fever ranging from 38 °C to 40 °C
Headache, often frontal or retro‑orbital
Myalgia affecting large muscle groups
Generalized fatigue and malaise
Chills and sweats

If laboratory testing confirms a specific rickettsial or Borrelia infection, the appropriate disease‑specific code (e.g., A69.2 for Lyme disease, A75.3 for spotted fever group rickettsiosis) should be added alongside W75.0. When only nonspecific flu‑like symptoms are present, the symptom code R50.9 (fever, unspecified) or R53.1 (weakness) may be used in conjunction with the external cause code.

Accurate coding ensures proper reimbursement, epidemiological tracking, and facilitates appropriate follow‑up for potential complications such as meningitis or arthritis that may develop after the initial flu‑like phase.

Swelling or Redness at the Bite Site

The appropriate ICD‑10‑CM identifier for a tick bite in an adult patient is W75.0 – Contact with or exposure to tick.

Swelling or redness at the bite site typically appears within hours to a few days after the encounter. The reaction may be limited to a localized erythematous halo, occasionally accompanied by edema that extends a few centimeters beyond the bite margin. In some cases, the area becomes tender or pruritic, and a central punctum may be visible.

For accurate coding, combine the primary exposure code (W75.0) with a symptom code that reflects the observed reaction:

R22.0 – Localized erythema (redness)
R22.1 – Localized swelling (edema)

Both codes may be reported simultaneously when both signs are present.

Documentation should include:

Date and location of the tick exposure.
Precise description of the skin changes (extent of erythema, degree of swelling, presence of pain or itching).
Any interventions performed (e.g., removal of the tick, topical treatment).

Including these details ensures that the clinical picture is fully captured and that the billing record reflects both the exposure and its dermatologic manifestations.

Prevention and Removal Strategies

Tick Repellents

Tick repellents constitute the primary preventive measure against arthropod bites that may later be recorded under the ICD‑10 classification for adult tick encounters. Effective formulations contain active substances such as DEET (N,N‑diethyl‑m‑toluamide), picaridin, IR3535, or oil of lemon eucalyptus, each providing a defined duration of protection calibrated to concentration levels. Application guidelines recommend covering exposed skin and clothing, re‑applying after swimming, sweating, or after the stipulated time interval indicated on the product label.

Key considerations for adult users include:

Selection of a repellent with at least 20 % DEET or equivalent picaridin concentration for extended outdoor activity.
Avoidance of application on irritated or broken skin to reduce dermal irritation risk.
Preference for formulations approved by regulatory agencies (e.g., EPA, CDC) to ensure safety and efficacy.

Consistent use of repellents reduces the incidence of tick attachment, thereby diminishing the frequency of clinical presentations that would be coded as “bitten or stung by insects” (ICD‑10 code W57.0) for adult patients. Preventive strategies also lower the probability of secondary complications such as Lyme disease, which carries distinct coding (e.g., A69.2).

Incorporating repellents into routine protective practices aligns with public‑health recommendations and directly impacts the epidemiology of tick‑related diagnoses recorded in medical databases.

Proper Tick Removal Techniques

The clinical classification for a tick bite in an adult is recorded under ICD‑10‑CM code A92.1. Accurate removal of the attached arthropod reduces the risk of pathogen transmission and tissue damage.

Effective removal requires the following steps:

Use fine‑point tweezers or a specialized tick‑removal tool; avoid blunt objects.
Grasp the tick as close to the skin surface as possible, securing the head and mouthparts.
Apply steady, downward pressure; pull straight out without twisting or jerking.
Inspect the bite site for retained mouthparts; if any remain, remove them with tweezers.
Disinfect the area with an antiseptic solution such as povidone‑iodine or alcohol.
Place the tick in a sealed container for identification if needed; do not crush it.
Record the encounter in the patient’s chart, noting the ICD‑10‑CM code and any symptoms.

These procedures align with public‑health recommendations and minimize complications associated with tick exposure.