ICD-10 code changes for 2027: What coders and billers need to know

The ICD-10-CM code set effective October 1, 2026—commonly referred to in the industry as the "2027 update," since it covers the coding year ahead—brought 209 total changes: 190 new codes, 15 deletions, and 4 revisions.

That's a sharp drop from last year's 544 changes, giving coders a comparatively quiet year to catch up on documentation and payer requirements before the next cycle.

A quick note on counting: if you look this up elsewhere and get a different total, that's normal. Some sources include codes released mid-year, and others group parent and child codes differently. Our totals reflect the full October 1 release.

Four chapters accounted for most of the activity:

• Injury, poisoning, and external causes (S00–T88): 75 changes (60 additions, 15 deletions), largely reorganizing toxic effect codes for industrial solvents and adulterants
• Pregnancy, childbirth, and the puerperium (O00–O9A): 44 new codes, the majority tied to vanishing twin syndrome, plus more specific location codes for ectopic pregnancy
• Musculoskeletal system (M00–M99): 31 new codes, largely expanding the "other osteomyelitis" category with laterality and body-site specificity, plus new laterality options for plantar fasciitis
• Factors influencing health status (Z00–Z99): 17 changes, including new BMI codes and new codes for gender transition history

A handful of the new codes describe conditions that may be unfamiliar even to experienced coders. Knowing what they mean, not just their code values, makes it easier to spot them in documentation and query providers when something doesn't line up:

• Glanzmann thrombasthenia (D69.11): a rare inherited bleeding disorder in which platelets can't clump together to form clots
• Brugada syndrome (I49.81): an inherited cardiac condition caused by a defect in the heart's ion channels, associated with dangerous arrhythmias and sudden cardiac death
• Odontogenic sinusitis (J34.830–J34.839): sinus inflammation caused by a dental infection or dental procedure, now broken out by sinus location
• Carbuncle of the flank (L02.237): a new laterality-adjacent code rounding out last year's expansion of flank-specific codes
• Lynch syndrome (QA1.71) and BRCA1/BRCA2 mutation codes (QA1.790, QA1.791): inherited conditions that significantly raise lifetime cancer risk, now with their own dedicated codes rather than being folded into general family-history categories
• Li-Fraumeni syndrome (QA1.792): a rare inherited disorder linked to early-onset breast cancer, brain and central nervous system tumors, and several other cancer types
• Loeys-Dietz syndrome (Q87.A): an inherited connective tissue disorder affecting the vascular system throughout the body

Vanishing twin syndrome describes the early loss and reabsorption of one fetus in a multiple pregnancy, while the remaining fetus or fetuses continue to develop.

Previously, ICD-10 had no dedicated way to capture this.

The new O31.4- series changes that, with codes built around two variables: the trimester in which the loss occurred (first, second, third, or unspecified) and which fetus remains, using the 7th character to identify the surviving fetus by number. The result is a large block of codes, but a narrow underlying concept—most of the volume comes from covering every trimester-and-fetus combination, not from new clinical scenarios.

The T52 and T59 code ranges were restructured for 2027 to add more specific toxic-effect codes for substances like alkenes and cycloparaffins (common in adhesives, paints, and industrial solvents) and hexamethylene diisocyanate (used in automotive spray painting and industrial coatings)—both of which show up in occupational exposure cases and workers' compensation claims.

T65.85- covers toxic effects of medetomidine, a veterinary sedative that has increasingly been identified as an additive in illicit fentanyl. It mimics fentanyl's sedative effect and has been showing up in overdose and emergency department cases, which is likely why it earned a dedicated code this cycle rather than falling under a general "other substance" category.

For the full, authoritative list of additions, deletions, and revisions, coders can reference the CMS ICD-10-CM files, which are published free of charge each year, or the CDC/NCHS ICD-10-CM page for the official code set and guidelines.

For background on any unfamiliar hereditary condition mentioned above, the National Organization for Rare Disorders maintains plain-language overviews that are useful for chart review and provider queries alike.