What Does ICD-10 Code F43.0 Mean?
ICD-10-CM code F43.0 designates acute stress reaction — a transient psychological disturbance arising directly from exposure to an exceptionally stressful event, with symptoms that develop within hours and resolve within days or, at most, one month. The code is valid and billable for fiscal year 2026 with no revisions to its description or validity status.
Key attributes of this code at a glance:
- Billable/valid in ICD-10-CM for all claim dates on or after October 1, 2015
- Classified under Chapter 5: Mental, Behavioral and Neurodevelopmental Disorders (F01–F99), subcategory F43
- Grouped to MS-DRG 880 (Acute Adjustment Reaction and Psychosocial Dysfunction) for inpatient claims
- Applicable in both inpatient and outpatient settings when clinical documentation supports the diagnosis
- No seventh-character extension required
What Conditions and Diagnoses Does F43.0 Cover?
F43.0 captures a cluster of acute, time-limited stress responses that follow a traumatic or overwhelming stressor. All of the following clinical presentations and synonymous terms map to this single code:
- Acute crisis reaction
- Acute reaction to stress (including psychological shock following an accident or assault)
- Combat and operational stress reaction (used for military personnel following battlefield exposure)
- Combat fatigue (within the acute presentation window)
- Crisis state with dissociative features
- Psychic shock — brief, self-limiting psychological disorganization following a precipitating event
What Does F43.0 Specifically Exclude?
The ICD-10-CM tabular includes important exclusionary notes. Do not assign F43.0 for:
- Post-traumatic stress disorder (F43.10–F43.12) — when symptom duration exceeds one month
- Adjustment disorders (F43.20–F43.29) — when symptoms are tied to life stressors rather than a discrete traumatic event
- Dissociative disorders (F44.–) — when dissociation is the primary presenting feature, not a secondary symptom
- Acute stress disorder per DSM-5 used as a stand-alone clinical diagnosis without ICD-10-CM mapping confirmation — note that DSM-5 maps “Acute Stress Disorder” to F43.0, but the symptom window criteria differ slightly (see below)
When Is F43.0 the Right Code to Use?
Use F43.0 when the following criteria are met in the documentation. Apply them in sequence before assigning the code:
- Confirm a discrete traumatic stressor is documented — a specific event involving actual or threatened death, serious injury, or sexual violation (not generalized life stress).
- Verify symptom onset occurred within hours of the triggering event.
- Confirm the symptom duration does not exceed one calendar month from the event date. If documentation shows persistence beyond one month, reassign to F43.10–F43.12 (PTSD).
- Confirm the presenting symptoms include at least some combination of: intrusive recollections, dissociation, hyperarousal, avoidance, or negative mood — consistent with either ICD-10 or DSM-5 criteria.
- Rule out a more specific code — if the provider documents a diagnosable condition like panic disorder (F41.0) or a depressive episode (F32.–), that more specific code takes precedence.
- Assign external cause codes as appropriate (e.g., Y93.–, V-codes, or assault codes) to provide the clinical context for the stressor.
How Does F43.0 Differ From F43.10 (PTSD, Unspecified) and F43.22 (Adjustment Disorder With Anxiety)?
This is the single most common point of confusion auditors and compliance reviewers flag in behavioral health claims.
| Feature | F43.0 Acute Stress Reaction | F43.10 PTSD, Unspecified | F43.22 Adjustment Disorder With Anxiety |
|---|---|---|---|
| Triggering stressor type | Discrete traumatic event (life-threatening) | Discrete traumatic event (life-threatening) | Any significant life stressor, not necessarily traumatic |
| Symptom onset | Immediate (hours to days) | Delayed (weeks to months possible) | Within 3 months of stressor |
| Maximum symptom duration | 1 month | Chronic/no upper limit | 6 months (unless stressor is ongoing) |
| DSM-5 equivalent | Acute Stress Disorder | PTSD | Adjustment Disorder |
| Dissociation required? | Common but not mandatory | Not required | Not expected |
| Code first/sequencing rules | External cause code recommended | External cause code recommended | External cause code optional |
In practice, coders frequently encounter situations where a provider documents “acute stress” without specifying duration. In these cases, query the provider before assigning F43.0 — defaulting to this code without confirmed symptom timeline is a common audit trigger.
What Documentation Is Required to Support F43.0?
What Must the Provider Document in the Clinical Notes?
A claim for F43.0 is at significant audit risk without the following elements clearly present in the medical record:
- Identification of the precipitating traumatic event — documented by name or description (e.g., “motor vehicle collision,” “witnessed workplace shooting,” “sexual assault”)
- Date and approximate time of the event — to establish the acute onset window
- Symptom onset timing — documented relative to the event (e.g., “symptoms began within 2 hours of the incident”)
- Specific symptom description — at least three to four symptoms listed (dissociation, intrusive recollections, hyperarousal, avoidance, negative affect)
- Symptom duration statement — provider must indicate that symptoms are expected to be, or have been, time-limited (less than one month)
- Functional impairment notation — confirmation that symptoms caused clinically significant distress or impairment in daily functioning
- Differential diagnosis exclusion — documentation ruling out substance intoxication/withdrawal, a general medical condition, or a more specific psychiatric disorder
Which Diagnostic or Lab Results Support F43.0?
Unlike many medical diagnoses, F43.0 is primarily supported through clinical evaluation rather than laboratory testing. Supporting evidence may include:
- Standardized screening instruments (e.g., Acute Stress Disorder Scale [ASDS], Stanford Acute Stress Reaction Questionnaire [SASRQ]) documented in the assessment
- Structured clinical interview notes reflecting DSM-5 or ICD-10 diagnostic criteria
- Trauma history documentation from the intake assessment
- Mental status exam confirming dissociative symptoms, hypervigilance, or emotional blunting at time of evaluation
What Is the Documentation Standard for Inpatient vs. Outpatient Settings?
| Documentation Element | Outpatient (Physician/Therapist Office) | Inpatient (Psychiatric Unit or ED) |
|---|---|---|
| Diagnosis authority | Licensed provider (MD, DO, LCSW if state-permitted for coding) | Attending physician required for final diagnosis |
| Coding basis | Confirmed diagnosis only — not “rule out” or “probable” | Confirmed AND probable/suspected diagnoses may be coded per ICD-10-CM Official Coding Guidelines Section II.H |
| Sequencing | F43.0 as principal/first-listed if primary reason for visit | May be secondary to a physical trauma code if hospitalized for injury with psychological sequelae |
| External cause codes | Highly recommended; payer-dependent | Required in many facility coding policies |
How Does F43.0 Affect Medical Billing and Claims?
F43.0 generates unique billing considerations compared to chronic mental health codes. Key points for revenue cycle teams:
- Medical necessity must be supported by documentation that the stressor was a qualifying traumatic event — vague “stress” claims without a trauma precipitant are frequently denied
- Commercial payers often require crisis intervention documentation (e.g., safety assessment, stabilization plan) when this code is submitted with emergency or intensive outpatient services
- Telehealth billing for F43.0 is generally covered under behavioral telehealth parity laws, though documentation requirements are identical to in-person visits
- This code does not require a prior-period diagnosis — it is always a new, event-driven clinical presentation
What CPT or Procedure Codes Are Commonly Billed With F43.0?
| CPT Code | Description | Typical Billing Context With F43.0 |
|---|---|---|
| 90837 | Psychotherapy, 60 min | Outpatient individual therapy session following acute trauma |
| 90839 | Psychotherapy for crisis, first 60 min | Emergency crisis intervention following the traumatic event |
| 90840 | Psychotherapy for crisis, each additional 30 min | Crisis stabilization requiring extended session |
| 90792 | Psychiatric diagnostic evaluation with medical services | Initial assessment when prescriber evaluates for medication needs |
| 99213–99214 | Office visit, established patient | Primary care or ED follow-up for stress-related somatic complaints |
| H0031 | Mental health assessment (HCPCS) | Community mental health center evaluations; Medicaid-dependent billing |
Are There Any Prior Authorization or Coverage Restrictions?
- Most commercial payers do not require prior authorization for initial crisis-related evaluations, but ongoing therapy sessions may require PA after a defined number of visits
- Medicaid managed care plans vary significantly by state — some require a behavioral health authorization even for F43.0 crisis codes
- Medicare covers F43.0-related services under the behavioral health benefit; coinsurance applies at 20% after Part B deductible
- Some payers restrict reimbursement for H0031 unless billed by a licensed community mental health center — verify LCD policies at the local MAC level via CMS Local Coverage Determinations
What Coding Errors Should You Avoid With F43.0?
Auditors consistently identify the following errors in claims coded with F43.0:
- Assigning F43.0 when symptoms exceed one month — this is the top error. Once symptom duration crosses the one-month threshold, PTSD codes (F43.1x) must be considered.
- Using F43.0 for general life stress or adjustment reactions — F43.0 requires a traumatic stressor, not an everyday stressor such as job loss or divorce (those belong in the F43.2x adjustment disorder subcategory).
- Omitting external cause codes — failing to add a companion external cause code (e.g., an assault code or accident code) leaves the stressor clinically undocumented and creates audit exposure.
- Coding “probable” acute stress reaction in outpatient settings — per ICD-10-CM Official Coding Guidelines, outpatient coders may only code confirmed diagnoses, not suspected ones.
- Sequencing F43.0 before a physical injury code — when a patient is admitted primarily for a physical trauma (e.g., fracture after assault), the injury code should be sequenced first with F43.0 as a secondary diagnosis.
- Using F43.0 for chronic combat exposure without acute onset — veterans experiencing cumulative combat stress without a discrete precipitating event are better served by F43.10 or F43.12.
What Do Auditors Look for When Reviewing Claims With F43.0?
- Symptom duration explicitly documented — absence of a duration statement is a top audit trigger
- Specificity of the traumatic event — vague language like “patient experienced stress” is insufficient
- Consistency between the diagnosis code and the CPT code billed — billing a routine 90837 session without crisis documentation when 90839 is submitted is a common mismatch flagged in clinical audits
- Lack of a differential diagnosis notation — auditors expect to see that PTSD and adjustment disorder were considered and ruled out
How Does F43.0 Relate to Other ICD-10 Codes?
| Related Code | Relationship to F43.0 | Key Clinical Distinction |
|---|---|---|
| F43.10 PTSD, Unspecified | Excludes 1 — mutually exclusive | Symptoms persist beyond one month |
| F43.11 PTSD, Acute | Excludes 1 — mutually exclusive | Symptoms last 1–3 months |
| F43.12 PTSD, Chronic | Excludes 1 — mutually exclusive | Symptoms persist 3+ months |
| F43.22 Adjustment Disorder with Anxiety | Related; different stressor threshold | Stressor need not be traumatic; no life-threat required |
| F41.0 Panic Disorder | Code separately if documented | Recurrent, unexpected panic attacks as a primary condition, not reactive |
| F44.– Dissociative Disorders | Excludes 1 in some presentations | Dissociation is primary, not reactive and secondary |
| F43.9 Reaction to Severe Stress, Unspecified | Less specific; use only when type cannot be determined | Acceptable when documentation is incomplete despite provider query |
What Is the Correct Code Sequencing When F43.0 Appears With Other Diagnoses?
- Inpatient: If admitted for a physical injury (e.g., traumatic brain injury, fracture), sequence the physical injury code first; F43.0 follows as an additional diagnosis.
- Outpatient: If the primary reason for the visit is the psychological reaction, F43.0 is the first-listed diagnosis.
- External cause codes (e.g., W-codes for falls, X-codes for assault, Y-codes for military operations) should be added after F43.0 or alongside any physical injury codes to document the mechanism of the traumatic event.
- Sleep disturbance (G47.00) may be coded as an additional diagnosis when insomnia is separately documented as a clinical problem requiring separate management — it does not automatically follow F43.0.
Real-World Coding Scenario — How F43.0 Is Applied in Practice
A 29-year-old emergency room nurse presents to an outpatient mental health clinic eight days after being physically assaulted by a patient during a shift. She reports nightmares about the event, hypervigilance at work, emotional numbness, and difficulty concentrating. The licensed clinical psychologist performs a diagnostic evaluation, documents that symptoms began within hours of the assault, confirms nine of fourteen DSM-5 Acute Stress Disorder criteria are met, and states that symptoms have been present for eight days with no indication they will persist beyond one month. No substance use or other psychiatric condition is identified.
Correct Code Application
- F43.0 — Acute stress reaction (primary diagnosis; confirmed by the provider with documented stressor, onset, symptom criteria, and duration expectation)
- Y04.0XXA — Assault by unarmed brawl or fight, initial encounter (external cause code documenting mechanism)
- CPT 90792 — Psychiatric diagnostic evaluation with medical services (if prescriber is involved) or 90837 (if psychotherapy session immediately followed the diagnostic evaluation)
Common Mistake in This Scenario
- Incorrect: Assigning F43.10 (PTSD, Unspecified) because the documentation mentions “trauma” and “hyperarousal”
- Why it fails: PTSD codes require symptoms to have persisted for more than one month. At eight days post-event with provider documentation of expected resolution, F43.10 is not clinically supported. Assigning it prematurely creates a false PTSD diagnosis in the patient’s medical record and exposes the claim to payer audit for lack of diagnostic criteria support.
Frequently Asked Questions About ICD-10 Code F43.0
Is ICD-10 Code F43.0 Still Valid in 2026?
ICD-10 code F43.0 is a valid, billable diagnosis code for fiscal year 2026 with no changes to its description, validity status, or code structure. Coders should verify annually against the ICD-10-CM Official Coding Guidelines released by CMS to confirm no revisions have been applied for the upcoming fiscal year.
What Is the Difference Between F43.0 and F43.10 (PTSD, Unspecified)?
F43.0 applies when acute stress symptoms are present for fewer than one month following a traumatic event, while F43.10 is assigned when the same category of symptoms persists beyond that one-month threshold. The codes are mutually exclusive — assigning both on the same claim is a coding error.
Can F43.0 Be Used for Combat Stress in Military Personnel?
Yes. The ICD-10-CM tabular explicitly includes “combat and operational stress reaction” and “combat fatigue” as included terms under F43.0, making this code appropriate for acute stress presentations in active-duty and veteran populations following a discrete combat event. If symptoms persist beyond one month, reassign to F43.11 (PTSD, Acute) or F43.12 (PTSD, Chronic) as appropriate.
Does F43.0 Require a DSM-5 Diagnosis to Be Billable?
F43.0 does not require a DSM-5 diagnosis — it is an ICD-10-CM code, and ICD-10-CM criteria govern billing in the United States. However, because DSM-5 maps its “Acute Stress Disorder” diagnosis to F43.0, many providers use DSM-5 criteria to establish clinical support for the code. Note that ICD-10-CM allows symptom duration up to one month, while DSM-5 Acute Stress Disorder specifies a minimum of three days — this discrepancy can create documentation confusion worth proactively addressing in clinical and coding workflows.
What Happens If F43.0 Is Not Documented With a Duration Statement?
A claim coded with F43.0 that lacks a documented symptom duration is a significant audit risk. Payers and auditors cannot confirm that PTSD codes were appropriately ruled out without a duration statement, making the claim vulnerable to downcoding or denial. The ICD-10-CM Official Coding Guidelines and standard coding audit preparation best practices both recommend querying the provider when duration is absent from the record.
Is F43.0 Covered by Medicare?
F43.0-coded services are covered under Medicare Part B when billed by an eligible mental health provider (psychiatrist, psychologist, licensed clinical social worker, or nurse practitioner with behavioral health training). The patient is responsible for 20% coinsurance after the Part B deductible. Coverage of specific CPT codes billed alongside F43.0 (such as crisis intervention codes 90839/90840) follows standard Medicare behavioral health benefit rules, which coders can confirm through the CMS Medicare Benefit Policy Manual.
Key Takeaways
Every coder and biller working with F43.0 should keep these core points in hand:
- F43.0 is reserved exclusively for acute, time-limited stress reactions following a discrete traumatic event — never for chronic stress or routine adjustment reactions
- Symptom duration is the defining variable separating F43.0 from PTSD codes; one month is the clinical ceiling
- Documentation must specify the triggering event, onset timing, specific symptoms, and expected or confirmed duration
- In outpatient settings, only confirmed diagnoses may be coded — “rule out” or “probable” F43.0 may not be assigned
- External cause codes should accompany F43.0 whenever the mechanism of the traumatic event can be identified
- The DSM-5 to ICD-10-CM mapping aligns “Acute Stress Disorder” with F43.0, but the duration criteria differ — proactively reconcile this in your documentation query process
- CPT 90839/90840 (crisis psychotherapy) pairs naturally with F43.0 when the evaluation occurs in direct response to an acute crisis presentation
For deeper guidance on behavioral health coding audit preparation and related mental health billing documentation requirements, review the AHA Coding Clinic for ICD-10-CM/PCS and the annual ICD-10-CM guidelines update from CMS.