If you’ve ever trained with me, you’ve probably heard my running joke about altered mental status (AMS): “If it’s the last chart of the day, it just became the first chart of tomorrow.”

Why? Because AMS is one of the most complex, wide-open clinical presentations you’ll encounter. Patients often arrive with multiple competing conditions, and the inpatient workup frequently becomes a process of elimination. Coders must navigate unclear documentation, overlapping symptoms, and – in many cases – payers ready to issue clinical validation denials.

That’s exactly why AMS is a high-risk, high-confusion diagnosis across organizations. And it’s also why coders need a clear approach to identifying what AMS is – and what it is not.

Below are three of the most common pitfalls coders encounter when working with AMS-related documentation:

Mistake #1: Treating AMS as a Diagnosis Instead of a Symptom

Altered mental status (R41.82) is a sign/symptom code, not a definitive condition. Whenever AMS appears in the provider’s documentation, it should prompt one immediate question: What is causing the altered mental status?

Common culprits may include:

• Encephalopathy
• Sepsis
• Urinary tract infection (UTI)
• Diabetic ketoacidosis (DKA)
• Toxic exposures or medication effects
• Underlying neurocognitive or psychiatric conditions

Identifying (or clarifying) the underlying cause is essential for accurate coding and appropriate sequencing.

Mistake #2: Defaulting to “G93.49 Other Encephalopathy” Too Quickly

Encephalopathy is frequently the underlying cause of AMS—but which type?
Metabolic, toxic, hypertensive, hepatic, anoxic, or a combination?

Not every case fits neatly into “other encephalopathy.” Coders should know when documentation supports a more specific option and when a provider query is needed. Because different encephalopathy types carry different sequencing rules and coding implications, specificity matters.

Mistake #3: Confusing Delirium and Encephalopathy

Although both conditions can present with AMS, delirium and encephalopathy are not interchangeable:

• Delirium usually fluctuates (waxing/waning) and may respond to antipsychotics.
• Encephalopathy tends to be more steady, with treatment focused on addressing the underlying physiological disturbance.

Accurately distinguishing the two is critical to code assignment, query strategy, and preventing denials.

Want to Clear the Brain Fog?

These three issues only scratch the surface. AMS coding involves nuance, clinical context, and a solid understanding of encephalopathy types, differential diagnoses, and sequencing rules.

If you want to strengthen your skills—and avoid the pitfalls that lead to coding errors and denials—join us for our upcoming webinar: “Clearing the Brain Fog Around Coding Altered Mental Status.”

We’ll break down the clinical concepts, documentation challenges, and coding strategies you need to feel confident tackling even the most complicated AMS cases.

Ready to turn AMS from your “first chart of tomorrow” into an opportunity for accuracy? Register today!