Gastroenterology Coding Alert

Do not report a celiac disease ICD-10-CM code unless the Dx is confirmed.

Do you know what celiac disease is? An autoimmune condition triggered by gluten may sound straightforward on the surface, but when it comes to medical coding, it can get complicated quickly. The diagnosis often unfolds over multiple visits, involves both serologic testing and biopsy, and may include long-term management and follow-up.

So, what should you do? As the gastroenterology coder, your role is to accurately reflect where the patient is in their diagnostic or treatment journey, while making sure claims are supported, compliant, and paid.

This article will walk you through how to code celiac disease step-by-step, from suspected disease to confirmed diagnosis and ongoing care, using clear examples you can apply right away.

Understand the Clinical Picture (and Why It Matters)

Celiac disease is an autoimmune disorder in which ingestion of gluten leads to damage in the small intestine. Because of this, patients may present with classic gastrointestinal (GI) symptoms (diarrhea, bloating, weight loss), non-GI symptoms (anemia, fatigue, osteoporosis), or no symptoms at all.

Make note: You should not code confirmed celiac disease until it is actually diagnosed.

Many claims get denied or flagged because coders jump straight to a definitive diagnosis code too early.

Identify ICD-10-CM Coding for Celiac Disease

Once the provider documents a confirmed diagnosis, the correct ICD-10-CM code is K90.0 (Celiac disease). To reiterate once more — you should only use this code after appropriate diagnostic confirmation (typically biopsy, sometimes supported by serology and clinical judgment).

Use K90.0 for:

• Established celiac disease
• Follow-up visits for dietary management
• Monitoring complications related to celiac disease

Code Suspected or Possible Celiac Disease (Before Diagnosis)

If the patient is being evaluated for celiac disease but does not yet have a confirmed diagnosis, do not use K90.0. Instead, you’ll code based on:

• Symptoms
• Abnormal findings
• Screening or testing encounters

Common coding choices include:

• R19.7 (Diarrhea, unspecified)
• R14.0 (Abdominal distension (gaseous))
• R63.4 (Abnormal weight loss)
• D50.9 (Iron deficiency anemia, unspecified)
• Z13.810 (Encounter for screening for upper gastrointestinal disorder)

Your diagnosis code must match what is documented during the visit, not what you expect the outcome to be.

What About Coding for Diagnostic Testing?

Celiac disease workups usually start with blood tests. Common CPT^® codes include:

• 82784 (Gammaglobulin (immunoglobulin); IgA, IgD, IgG, IgM, each)
• 83516 (Immunoassay for analyte other than infectious agent antibody or infectious agent antigen; qualitative or semiquantitative, multiple step method)
• 86008 (Allergen specific IgE; quantitative or semiquantitative, recombinant or purified component, each) (sometimes used in broader evaluations)

Choosing the correct code depends on:

• The specific antibody tested (for example, tissue transglutaminase IgA [tTG-IgA], endomysial antibody [EMA], deamidated gliadin peptide [DGP])
• The laboratory methodology
• The lab’s test menu

Coder tip: These tests are typically billed by the laboratory performing the testing, not the physician practice.

What If My Doctor Orders Confirmatory Testing?

If serology is positive or suspicion remains high, patients will often undergo an upper endoscopy with small bowel biopsy. You’ll report 43239 (Esophagogastroduodenoscopy, flexible, transoral; with biopsy, single or multiple) for this procedure.

Pathology is billed separately by pathology providers using 88305 (Level IV - Surgical pathology, gross and microscopic examination … Small intestine, biopsy …).

Diagnosis coding at this stage: your diagnosis codes often still reflect symptoms or abnormal findings unless the provider documents confirmed celiac disease.

How to Code the Office Visit

Before a celiac disease diagnosis, if the provider is evaluating symptoms or reviewing abnormal labs, you’ll report an evaluation and management (E/M) code, such as 99202-99205 (Office or other outpatient visit for the evaluation and management of a new patient …) for new patients or 99212-99215 (Office or other outpatient visit for the evaluation and management of an established patient …) for established patients.

Your diagnosis codes should still reflect:

• Symptoms
• Abnormal labs
• Screening or evaluation

Because celiac disease is only suspected and not confirmed, you do not report the celiac disease ICD-10-CM code.

Once celiac disease is confirmed and documented, follow-up visits can be coded with a diagnosis code of K90.0. You’ll use the same E/M service codes. These visits often involve:

• Dietary counseling
• Monitoring symptom improvement
• Managing complications (nutritional deficiencies, bone health)

Nail Down Nutrition Counseling and Care Coordination

Many patients with celiac disease are referred to a registered dietitian.

Common CPT^® codes include:

• 97802 (Medical nutrition therapy; initial assessment and intervention, individual, face-to-face with the patient, each 15 minutes)
• 97803 (… re-assessment and intervention, individual, face-to-face with the patient, each 15 minutes)

These services are often billed separately and may have specific coverage rules depending on the payer.

Avoid These Common Coding Pitfalls

Do not code confirmed celiac disease based on:

• Positive blood test alone (unless provider documents diagnosis)
• Patient-reported history without confirmation

Do not use food allergy codes. Celiac disease is not a food allergy. Avoid codes like Z91.018 (Allergy to other foods) or allergy-related ICD-10-CM codes.

Do not mismatch your diagnosis and service codes. Make sure:

• Screening codes support screening services;
• Symptom codes support diagnostic evaluations; and
• K90.0 supports ongoing management.

Documentation Tips That Make Your Job Easier

Encourage your providers to document a clear diagnostic status (suspected vs. confirmed). You’ll also need to look at any potential test results reviewed. Watch out for assessment language (“consistent with,” “confirmed,” “ruled out”), and pay attention to the ongoing management plan.

The clearer the provider’s documentation, the stronger your coding position.

Takeaway

Coding for celiac disease isn’t difficult as long as you code the journey, not the destination. Your job is to reflect what is known at each point in care, not what’s likely or suspected.

Remember:

• Use symptom and screening codes during evaluation
• Use K90.0 only once celiac disease is confirmed
• Match diagnosis codes carefully to labs, procedures, and E/M services
• Watch for payer-specific rules on nutrition therapy and diagnostics

When done correctly, your coding supports accurate reimbursement, reduces denials, and ensures the patient’s medical record tells the patient’s story, one visit at a time.

Suzanne Burmeister, BA, MPhil, Medical Writer and Editor