ICD-10 Code for Change in Mental Status:

The ICD-10 code for change in mental status is R41.82 — altered mental status, unspecified. In the FY2026 ICD-10-CM tabular list ↗, R41.82 carries the inclusion term “change in mental status NOS” — so “change in mental status,” “altered mental status,” and “AMS” all resolve to the same code.

Note what R41.82 is not: it is not an F-code. It lives in Chapter 18 of ICD-10-CM (Symptoms, signs and abnormal clinical and laboratory findings, R00–R99), not in the mental and behavioral disorders chapter. That placement drives every rule on this page — R41.82 describes a finding, not a diagnosis, and it is only correct while the cause remains unestablished.

This page is part of our ICD-10 directory for behavioral health.

The answer: R41.82

R41.82 — Altered mental status, unspecified is a complete, billable code (no further characters required). The FY2026 tabular entry includes three Excludes1 notes that define its boundaries:

Excludes1 means never code together: if the chart supports stupor, diagnosed delirium, or a known cause, R41.82 does not belong on the claim alongside those codes.

The “due to known condition” exclusion is the one that does the most work. R41.82 is a placeholder for diagnostic uncertainty — the moment a provider documents why the patient’s mental status changed, the why becomes the code.

When NOT to use R41.82

Chapter 18’s ground rule appears in the ICD-10-CM Official Guidelines for Coding and Reporting ↗, Section I.C.18.a: symptom codes “are acceptable for reporting purposes when a related definitive diagnosis has not been established (confirmed) by the provider.” Section I.C.18.b adds that symptoms routinely associated with an established diagnosis should not be coded additionally.

In practice, R41.82 comes off the problem list when documentation establishes any of these:

• Delirium due to a physiological condition → F05. The FY2026 tabular instructs code first the underlying physiological condition for F05, and its inclusion terms cover acute confusional states and delirium superimposed on dementia. Alcohol withdrawal delirium is excluded from F05 and codes within the substance categories (e.g., F10.231) — see our F10 alcohol coding guide.
• Dementia → F01–F03. Vascular dementia (F01.-), dementia in other diseases classified elsewhere (F02.-), or unspecified dementia (F03.9-), each with behavioral-disturbance specificity in the current code set.
• Substance intoxication or withdrawal → F10–F19. A clouded sensorium during intoxication or withdrawal is coded within the substance category — intoxication, intoxication delirium, or withdrawal codes as documented. The F10–F19 family pages map these character-by-character.
• Encephalopathy → G93.4-. When the provider documents encephalopathy rather than (or in addition to) AMS — see the decision table below.
• A psychiatric diagnosis explaining the presentation → the F-code. Acute psychosis, severe mood episodes, and catatonia all have specific codes; AMS language in the chart is subsumed once the psychiatric diagnosis is established.

AMS at behavioral health facilities

Most R41.82 guidance is written for emergency departments. Behavioral health facilities meet the code in different workflows, and the coding posture differs at each point:

• Intake and medical clearance. Admission assessments to detox or residential programs document baseline mental status. When a referral arrives with “AMS” in the ED paperwork, the receiving facility should not import R41.82 onto its own claims if its providers establish a cause (intoxication, withdrawal, psychiatric decompensation) — code what your provider documents.
• Detox-unit mental status changes. A client in withdrawal management who becomes confused or disoriented is a clinical event first and a coding event second. If the provider attributes the change to withdrawal, code the withdrawal (with delirium where documented) in the F10–F19 structure; R41.82 applies only in the window where the cause is genuinely undetermined.
• Medical escalation and ED transfer. When a mental status change triggers a transfer for medical workup, R41.82 is often the honest code for the sending facility’s documentation of the event — the definitive diagnosis happens at the hospital. Document onset, observed changes from baseline, vitals, and the decision rationale.
• Why payers won’t anchor BH level of care on R41.82. Behavioral health medical necessity runs on treatable psychiatric and substance use diagnoses. A symptom code with an unestablished cause supports a medical workup, not a psychiatric level of care — so R41.82 as the primary diagnosis on a residential or PHP claim is effectively a denial request. It can appear as a secondary code documenting an event during the stay; it cannot carry the stay.

R41.82 vs. encephalopathy vs. delirium

The classic coder triangle. All three terms can describe the same confused patient; the code follows the provider’s documented diagnosis:

Documentation queries are legitimate here: if the clinical picture in the record supports encephalopathy or delirium but the provider wrote only “AMS,” a query — not coder inference — is the compliant route to the more specific code.

Documentation requirements

Whether R41.82 stays on the claim or graduates to a definitive diagnosis, the note should capture:

That packet does double duty: it supports the symptom code while the cause is open, and it supports the definitive code — and the medical-necessity story — once the cause is found.

• Onset and course — abrupt vs. gradual, fluctuating vs. fixed.
• Baseline comparison — what the patient’s normal cognition and behavior look like, and who confirmed it (family, residential staff, prior records). “Altered” only means something against a stated baseline.
• Observed findings — orientation, attention, level of arousal, behavior; a brief structured tool strengthens the record.
• Suspected etiology and workup — what was considered (substances, medications, infection, metabolic causes, psychiatric decompensation) and what was ordered or ruled out.
• Disposition rationale — continued observation, psychiatric evaluation, or medical transfer, and why.

Worked examples

Three fictional examples showing how the rules play out in behavioral health settings:

Example 1 — R41.82 holds. A 58-year-old client in a residential SUD program, six days post-admission and past acute withdrawal, becomes intermittently confused over an afternoon. Vitals are unremarkable; no new medications; the nurse documents disorientation to time, fluctuating attention, and a clear deviation from the client’s documented baseline. The provider documents “altered mental status, etiology unclear; medical workup initiated” and arranges ED transfer. Code: R41.82 for the facility’s documentation of the event — no cause was established before transfer.

Example 2 — R41.82 comes off. Same scenario, but the client is on day two of admission and the provider documents “confusion and disorientation consistent with sedative withdrawal; CIWA-B elevated; withdrawal management adjusted.” The cause is established. Code: the sedative withdrawal code from the F13 structure — R41.82 would now violate its own “due to known condition” Excludes1 note. See the F13 family page.

Example 3 — the hospital answers, the code follows. The Example 1 client returns from the ED with a discharge summary documenting metabolic encephalopathy from hyponatremia. Subsequent facility documentation that addresses the resolved event references the established diagnosis ( G93.41 with the electrolyte disorder), not R41.82.

Common coding errors

For behavioral health teams, the practical challenge is making this documentation routine at intake and during stays. An EHR with structured mental-status fields in its assessment and shift-note templates makes the baseline-comparison record automatic rather than aspirational. ’s EHR includes customizable assessment and progress-note templates for exactly this.

Request a Demo: contact us.

• Carrying R41.82 forward after diagnosis. The most frequent error: AMS coded at intake, cause established on day three, R41.82 still riding on claims at week two. Build diagnosis review into utilization-review touchpoints.
• Coding R41.82 with R40.- or a documented delirium. Both pairings violate Excludes1 notes. Pick the code the documentation supports.
• Using R41.82 for chronic confusion. Long-standing cognitive impairment is not an acute mental-status change — it points to the dementia and cognitive-deficit code families, not a Chapter 18 symptom code.
• Letting the ED’s code become your code. Referral paperwork codes describe the sending provider’s documentation, not yours. Code what your own providers establish.

Sources: FY2026 ICD-10-CM code set and tabular list ↗ (CMS, effective Oct 1, 2025); ICD-10-CM Official Guidelines for Coding and Reporting, FY2026 ↗, Sections I.C.18.a–b; CDC NCHS ICD-10-CM ↗. Accessed June 2026.

Reference tables

Common questions

Official sources

• FY2026 ICD-10-CM tabular listcms.gov
• ICD-10-CM Official Guidelines for Coding and Reportingcms.gov
• CDC NCHS ICD-10-CMcdc.gov