Ultimate guide to ICD-10-CM Codes F01-F99

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If you have spent any time managing a behavioral health practice, you already know the frustration. A claim comes back denied. Your biller digs into it. The code was too vague  or worse, it was the right code for last year but not this one. Meanwhile, the provider spent 60 minutes with a patient who genuinely needed care, and now that session is sitting in accounts receivable limbo.

This is the reality of billing mental and behavioral health services. The F01-F99 code range Chapter 5 of ICD-10-CM, is where that reality lives. Getting it right is not just a billing department problem. It is a clinical documentation problem, a training problem, and ultimately a revenue problem that lands on your desk.

This guide is written for the people actually managing those problems: practice managers, administrators, and the providers whose notes either make or break a claim.

When ICD-10 replaced ICD-9, mental health coding did not just get an upgrade but it got a complete overhaul. The old system had roughly 290 codes for psychiatric and behavioral conditions. The current F-category has over 1,500. That is not bureaucratic excess. That's specificity that payers now expect and, increasingly, require.

Each F-code on a claim is telling a story to the insurance company, here is what this patient has, here is how bad it is, here is why this level of care was required. When this story is not complete, or not consistent with what the provider has documented, the claim will not go through but when it is precise, specific and well-supported, it goes through cleanly.

The 2026 ICD-10-CM updates took effect on October 1, 2025. If your staff has not reviewed these changes, particularly the new codes for eating disorder subtypes and rumination disorder in adults the that is a conversation worth having sooner rather than later.

Before you can use F-codes effectively and accurately, you will need to understand their structure. It iss not complicated, but it matters.

Every F-code starts with "F", as this is obvious. The first three characters form the category. F32, for instance, is the category for major depressive disorder. Add a decimal and a fourth character, you then get to the actual diagnosis code, F32.0 is mild, F32.1 is moderate, F32.2 is severe without psychotic features and so on. Some codes go further with a fifth or sixth character for even greater clinical detail.

Here's the rule that trips up a lot of practices: most behavioral health codes require at least four characters. Stopping at three, using F32 instead of F32.1,  will get your claim rejected. Payers don't just prefer the highest level of specificity. They expect it. If the documentation supports a more specific code and you didn't use it, that's a coding error, and it costs you.

The Major Code Categories and What They Cover

The F-range codes cover a broad range of circumstances. Here is how the broad categories are subdivided and what your documentation must support for each.

F01-F09: Mental Disorders Due to Known Physiological Conditions 

This category includes such things as vascular dementia, dementia related to Alzheimer’s disease, and personality changes due to brain injury or other medical reasons. The important aspect of your documentation in this category is that there must be a clear clinical connection made between the mental issues and the underlying physical problem. Otherwise, the code would not be valid.

F10–F19: Substance-Related Disorders 

This is one of the most commonly billed and commonly miscoded diagnoses. The fourth digit in this diagnosis differentiates abuse (F10.1) from dependence (F10.2), and this difference has both clinical and financial implications. When a patient's chart shows both, it is clear from the 2026 guidelines that only the dependence should be coded, as it is the more serious of the two diagnoses. The substance, the pattern of use, and any complications should be specified. Incomplete coding for substance use is a frequent trigger for an audit.

F20–F29: Schizophrenia Spectrum and Other Psychotic Disorders 

Schizophrenia, schizoaffective disorder, delusional disorder - these diagnoses require documentation of symptoms. General mentions of "psychotic symptoms" do not help with specificity. The records should indicate what the provider actually evaluated.

F30–F39: Mood Disorders 

Major depression and bipolar disorder reside here, and this is probably where you will see the most problems with billing. Severity, episode pattern, and psychotic features all matter. The clinician who writes out "depression" without specifying severity or episode pattern is leaving you with an unspecified code, and unspecified codes are becoming increasingly troublesome with commercial carriers.

F40–F48: Anxiety and Stress-Related Disorders 

Generalized anxiety disorder, panic disorder, PTSD, OCD, adjustment disorders, this list covers a wide range of disorders and when it comes to PTSD, then the difference between acute (F43.11) and chronic (F43.12) is important for coding. The records must support your choice and the patient with symptoms for more than a month after a traumatic event, is not the same as the patient with symptoms for years.

F50–F59: Behavioral Syndromes

Eating disorders, sleep disorders, and sexual dysfunction. The 2026 revisions include new specificity regarding eating disorders, which means if you see patients with these conditions, your staff must be up to date on the new codes.

F60–F69: Personality Disorders 

Borderline, paranoid, antisocial, and other personality patterns. These require documentation of long-standing behavioral patterns, not just acute presentation. A single session note rarely provides sufficient support for a personality disorder code. Your clinicians need to be building that picture across encounters.

F70–F79: Intellectual Disabilities 

Coded by the level of severity from mild (F70) to profound (F73). Straightforward, but requires documentation that actually characterizes the level.

F80–F89: Neurodevelopmental Disorders 

Autism spectrum disorder, specific learning disorders and developmental coordination disorder are classified here. ASD coding in particular has evolved, make sure your team is using current criteria.

F90–F98: Behavioral and Emotional Disorders with Onset in Childhood

ADHD is coded in this system as F90.0 for the inattentive type, F90.1 for the hyperactive-impulsive type and F90.2 for the combined type. This group also includes conduct disorders and oppositional defiant disorder. In pediatric and adolescent psychiatry, it is important to code the subtype correctly because this is directly related to medical necessity for treatment strategy.

For your reference, we have attached codes here that are common in behavioral health billing:

Let's be direct about the most common coding errors in behavioral health, because they are preventable and they're expensive.

• Defaulting to unspecified codes. F32.9 (major depression, unspecified), F41.9 (anxiety disorder, unspecified), F43.10 (PTSD, unspecified), these codes exist for situations where documentation genuinely cannot support a more specific type of diagnosis. They are not a shortcut for incomplete notes. Payers have become significantly more aggressive about scrutinizing unspecified codes and many commercial insurers are reducing reimbursement or outright denying claims that rely on them when more specific options exist. If your practice has a high volume of unspecified codes, that is a documentation training issue, not a coding issue. The problem sits upstream and at the point of the clinical encounter.

• Using outdated codes. ICD-10-CM updates every October 1st. A code that was valid on September 30th may not be valid on October 1st. Claims submitted with prior-year codes are automatically rejected. This isn't an appeals situation, it is a prevention situation. Your team needs a process for reviewing annual updates before they go live.

• Mismatching diagnosis and procedure codes. The diagnosis you bill must logically support the service you provided. A mild anxiety disorder code paired with intensive outpatient treatment will raise concerns. The clinical documentation needs to justify both the diagnosis and the level of care.

• Incorrect sequencing for comorbidities. When a patient has multiple diagnoses such as, depression and anxiety, PTSD and alcohol abuse and sequence them with the primary condition being treated first. The lead diagnosis signals to the payer what the encounter was primarily about. Get the sequencing wrong and you may undermine the medical necessity argument for the services billed.

• Using Z-codes as primary diagnoses. Z-codes document factors influencing health status i.e, family history, social circumstances and the like. They are secondary codes, full stop. Most payers will not accept them as the primary diagnosis on a behavioral health claim because they do not establish medical necessity. Leading with a Z-code is a reliable path to denial.

This is where the practice manager must have an honest discussion with the clinical team. Billing accuracy starts with the note.

For mood disorders, the documentation needs to capture severity, functional impairment, and episode pattern. "Patient reports feeling depressed" is not enough. "Patient describes persistent low mood for six weeks, difficulty maintaining employment, significant withdrawal from family relationships, and poor sleep, consistent with a moderate major depressive episode",  that is the note that supports F32.1.

For substance use disorders, document the substance, the pattern of use, whether tolerance or withdrawal is present, and the clinical complications. The difference between F10.1 and F10.2 hinges on what's in that note.

For individuals diagnosed with PTSD, the event or events leading to the diagnosis of PTSD should be noted, the length of time the individual has been exhibiting the signs of PTSD, and the signs of PTSD should be noted. If the signs of PTSD have been evident for longer than 30 days, this should be noted because F43.12 would be defensible in this case.

For personality disorder diagnoses, it should be noted that a single encounter or record does not support a diagnosis of a personality disorder. Patterns of behavior should be noted in several encounters to support your documentation of a personality disorder.

Three Real-World Coding Scenarios

Scenario 1: Anxiety and Depression Together

A 35-year-old shows up for outpatient therapy. The provider notes moderate depression during the first episode, along with generalized anxiety disorder. The notes mention a low mood, a lot of worry, trouble sleeping, and problems that are making it hard for him or her to work and maintain relationships.

The correct coding is F32.The main diagnosis is moderate major depressive disorder, single episode, labeled as F41.1, as secondary to generalized anxiety disorder. Both conditions are addressed and coded, with the primary one showing what the treatment is focused on.

Scenario 2: Alcohol Dependence with Secondary Depression

A patient struggling with alcohol dependence who also develops depression as a result. The assessment shows a simple dependence along with some mild depression linked to the substance use. The treatment focuses on alcohol dependence.

Correct coding is F10.20, as primary diagnosis (alcohol dependence, uncomplicated), F32.0, classified as secondary with mild major depressive disorder. Depression is real and well-documented, but the main focus of treatment guides the order of care.

Scenario 3: Chronic PTSD with Alcohol Abuse

A combat veteran is diagnosed with PTSD symptoms that have persisted for several years, nightmares, flashbacks, hypervigilance. He also reports that he drinks to cope, but does not meet the criteria for dependence.

The correct coding would be F43.12, as primary diagnosis, (PTSD chronic) and F10.10, as secondary which is (alcohol abuse, uncomplicated). The notes show the length of time, backing up the chronic classification. Alcohol use comes second because it happens as a result of the main condition, and isn’t the main thing being treated.

Even with clean coding, denials happen. How you respond determines whether you recover that revenue.

Denial code CO-16 means the payer needs more information or documentation. This is often a medical necessity issue, your codes are fine, but the clinical record doesn't adequately support them. Your appeal needs to extract the specific clinical findings from the notes and connect them explicitly to the diagnosis criteria and the level of service provided.

Denial code PR-49 indicates a non-covered diagnosis. This frequently occurs when Z-codes appear as primary diagnoses. The fix is usually re-sequencing, lead with the F-code and move the Z-code to secondary.

When appealing for medical necessity, be specific. Quote the symptom descriptions. Reference functional impairment. Show how the documented clinical picture meets the threshold for the coded diagnosis. Payers respond to concrete clinical evidence, not general arguments.

Always know your payer's appeal deadline and submit before it. A technically perfect appeal submitted one day late is a lost appeal.

Your diagnosis codes establish medical necessity. Your CPT codes describe the service delivered. Both have to be right, and they have to align with each other.

For psychiatric evaluations: CPT 90791 (without medical services) and CPT 90792 (with medical services). For individual psychotherapy: CPT 90832 (30 minutes), 90834 (45 minutes), 90837 (60 minutes). These are time-based codes, which means your documentation needs to reflect actual time spent. If you bill 90837, the note needs to support 60 minutes of psychotherapy. This is an audit area payers watch closely.

The F-code you pair with these CPT codes should reflect the condition being actively treated in that session. Consistency across the claim, diagnosis, procedure, and documentation, is what gets claims paid on the first submission.

ICD-10-CM updates annually. That is not a minor administrative note but it is an operational requirement. Here's what a well-run behavioral health practice has in place:

A process for reviewing annual code changes before October 1st each year. Not after claims start rejecting before. CMS publishes the updated code set in advance, and the American Hospital Association's Coding Clinic provides guidance on application. Both should be part of your annual billing calendar.

Regular internal audits of coded claims, specifically checking for unspecified code overuse, outdated codes, and diagnosis-procedure mismatches. Audits catch patterns before payers do. Finding that 30% of your depression claims use F32.9 is uncomfortable internally. Finding it during a payer audit is considerably worse.

Clinical documentation training that connects providers to billing outcomes. Many clinicians do not know that their note is the foundation of the claim. When they understand that "moderate depression" in a note translates to a specific code with specific reimbursement implications, note quality tends to improve.

Access to reliable code lookup tools for daily reference, ICD10Data.com and the AAPC Coder platform are both solid options. These are useful for quick verification, but they don't replace proper coding education. Use them to confirm; don't use them to learn.

Behavioral health billing is not forgiving of approximation. The F01-F99 range gives coders the tools to represent clinical reality with genuine precision but only if the documentation supports it and the coding reflects it accurately.

Your role as a practice manager is to close the gap between what providers document and what billers code. That means investing in training on both sides, building audit processes that catch errors early, and staying current with annual code updates. It also means having honest conversations when documentation doesn't meet the bar because every vague note is a potential denied claim.

The practices that do this well do not just have cleaner billing. They have better compliance posture, fewer audit risks, and more predictable revenue. That's worth the operational investment.

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