ICD-10 Code for Constipation: K59.00 and the Five Subtypes

K59.00 gets used constantly as a catch-all, and most of the time that's fine. But constipation actually has five distinct subtype codes, and a chart that already describes which kind is happening deserves the more specific one.

Constipation is one of the most frequently billed GI symptoms in primary care, and its code family is bigger than the single unspecified code most practices default to.

K59.00: Constipation, Unspecified

K59.00 covers constipation without a documented subtype — the default when the cause and pattern aren't further characterized. It's billable on its own and appropriate for a large share of visits, especially first-time presentations before any workup has happened.

The Subtype Codes

K59.01 — Slow transit constipation

K59.02 — Outlet dysfunction constipation

K59.03 — Drug induced constipation

K59.04 — Chronic idiopathic constipation

K59.09 — Other constipation

K59.03 is worth calling out specifically. Opioid-induced constipation and constipation from other medications is extremely common, and if the chart already names the causative drug, coding straight to K59.00 skips detail that's sitting right there in the note.

When the Subtype Codes Matter Most

Chronic constipation that's been through a workup — colonoscopy, transit studies, anorectal manometry — usually ends up with enough information to support K59.01, K59.02, or K59.04 instead of the unspecified code. Coding to the specific subtype once that workup exists is a more accurate reflection of what's actually documented, not just a technicality.

Common CPT Pairings

Constipation claims that go beyond a basic office visit sometimes involve a colonoscopy (45378) to rule out structural causes, particularly for new-onset constipation in older patients or when alarm symptoms are present alongside it.

Documentation Tips

The gap worth closing is simple: if the note already says "constipation, likely opioid-related" or "slow transit confirmed on prior testing," that detail should carry through to the code. Defaulting to K59.00 out of habit when a subtype is already documented understates what the chart actually supports.

Get a free practice audit and we'll check how often your constipation claims could move to a subtype code based on documentation that's already there.

Frequently Asked Questions

Is K59.00 billable? Yes, K59.00 is a billable, specific ICD-10-CM code for constipation, unspecified.

When should K59.03 be used instead of K59.00? Whenever a specific medication is documented as the cause — opioids are the most common trigger, but other drug classes can cause it too.

What's the difference between slow transit and outlet dysfunction constipation? Slow transit (K59.01) reflects delayed movement through the colon itself; outlet dysfunction (K59.02) reflects difficulty with the mechanics of evacuation despite normal transit time.

Does chronic constipation always need a workup before a subtype code applies? Not necessarily — a subtype can be documented clinically without formal testing, though workup results (transit studies, manometry) provide the strongest support for the more specific codes.

What triggers a colonoscopy for constipation? New-onset constipation in older adults, or constipation accompanied by alarm symptoms like weight loss or bleeding, typically prompts colonoscopy to rule out a structural cause.