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MS-DRG 100 · MDC 01 · Medical

MS-DRG 100: Seizures with MCC

Reviewed by QuickIntell RCM Editorial Team · Last reviewed

Data effective
Data currency: IPPS Table 5 FY2027 final rule (effective October 1, 2026); Definitions Manual v44 (effective October 1, 2026). Next CMS release: April 1, 2027 (v44.1 mid-year update), then the FY2028 final rule in August 2027.

Key facts for DRG 100

FY2027 relative weight
1.9240
Higher than 60% of all MS-DRGs
Change vs FY2026
-0.7%
FY2026 weight 1.9370
Geometric mean LOS
4.3 days
Arithmetic mean 6.2 days
MDC
01
Assignment of Diagnosis Codes
Severity level
with MCC (major complication or comorbidity)
Transfer policy
Post-acute transfer DRG

TL;DR

MS-DRG 100 is a medical group in MDC 01 (Assignment of Diagnosis Codes) at the highest-severity level of its family. CMS assigns it a FY2027 relative weight of 1.9240 with a geometric mean length of stay of 4.3 days and an arithmetic mean of 6.2. Its weight moved down 0.7% from FY2026 (1.9370). That weight is higher than 60% of all medical and surgical MS-DRGs. Its CC/MCC family (DRG 101) spans weights 0.8950 to 1.9240. The v44 Definitions Manual assigns it through 62 principal diagnosis codes.

What changed from FY2026 to FY2027

CMS recalibrates every MS-DRG weight annually from the prior year's MedPAR claims. For DRG 100 the FY2027 relative weight is 1.9240 against 1.9370 in FY2026, a fall of 0.67%.

FY2026 versus FY2027 payment factors for MS-DRG 100
MetricFY2026FY2027Change
Relative weight1.93701.9240-0.0130
Geometric mean LOS (days)4.34.3+0.0
Arithmetic mean LOS (days)6.36.2-0.1
Weights shown are the FY2027 final values after the 10% cap on year-over-year reductions where applicable.

CC and MCC family

DRG 100 shares its base definition with 1 other MS-DRG split by severity. The family's weights span 0.8950 to 1.9240, a 2.15× spread, which is the payment effect of documenting qualifying complications and comorbidities.

MS-DRGs in the same base group as DRG 100
DRGTitleFY2027 weightGMLOS
100Seizures with MCC1.92404.3
101Seizures without MCC0.89502.6

Grouper logic (v44 Definitions Manual)

Principal Diagnosis: 62 ICD-10 codes drive assignment to this group; the first 12 are shown.

Principal Diagnosis codes assigned to DRG 100 (sample)
ICD-10 codeDescription
G40001Localization-related (focal) (partial) idiopathic epilepsy and epileptic syndromes with seizures of localized onset, not intractable, with status epilepticus
G40009Localization-related (focal) (partial) idiopathic epilepsy and epileptic syndromes with seizures of localized onset, not intractable, without status epilepticus
G40011Localization-related (focal) (partial) idiopathic epilepsy and epileptic syndromes with seizures of localized onset, intractable, with status epilepticus
G40019Localization-related (focal) (partial) idiopathic epilepsy and epileptic syndromes with seizures of localized onset, intractable, without status epilepticus
G40101Localization-related (focal) (partial) symptomatic epilepsy and epileptic syndromes with simple partial seizures, not intractable, with status epilepticus
G40109Localization-related (focal) (partial) symptomatic epilepsy and epileptic syndromes with simple partial seizures, not intractable, without status epilepticus
G40111Localization-related (focal) (partial) symptomatic epilepsy and epileptic syndromes with simple partial seizures, intractable, with status epilepticus
G40119Localization-related (focal) (partial) symptomatic epilepsy and epileptic syndromes with simple partial seizures, intractable, without status epilepticus
G40201Localization-related (focal) (partial) symptomatic epilepsy and epileptic syndromes with complex partial seizures, not intractable, with status epilepticus
G40209Localization-related (focal) (partial) symptomatic epilepsy and epileptic syndromes with complex partial seizures, not intractable, without status epilepticus
G40211Localization-related (focal) (partial) symptomatic epilepsy and epileptic syndromes with complex partial seizures, intractable, with status epilepticus
G40219Localization-related (focal) (partial) symptomatic epilepsy and epileptic syndromes with complex partial seizures, intractable, without status epilepticus

Documentation and denial exposure

As a medical DRG, assignment depends on the principal diagnosis sequenced from the attending's documentation; a secondary condition sequenced first, or a symptom code in place of the confirmed diagnosis, changes the MDC or the DRG. Because this family splits by severity, auditors target CC and MCC capture: each secondary diagnosis must be documented as present, monitored, evaluated or treated during the stay to survive a DRG-validation review. Typical inpatient denial codes for this group: CARC 16 (claim lacks information needed to group the stay), CARC 50 (the admission or procedure is judged not medically necessary), CARC 97 (a service is bundled into the DRG payment).

How QuickIntell uses DRG 100 data

QuickCode groups inpatient encounters against the current v44 logic, flags CC and MCC candidates that lack supporting documentation, and shows the weight difference across the family before the claim drops. QuickScribe captures the attending's language that supports severity, and QuickRCM works DRG-validation denials with the grouper evidence attached.

Explore QuickCodeExplore QuickScribeBook a demo

Frequently asked questions — DRG 100

What is MS-DRG 100?

MS-DRG 100 is "Seizures with MCC", a medical Medicare Severity Diagnosis-Related Group in MDC 01, Assignment of Diagnosis Codes. Medicare pays inpatient stays grouped here at the hospital's base rate multiplied by the DRG relative weight.

What is the FY2027 relative weight for DRG 100?

The FY2027 relative weight is 1.9240 (IPPS final rule Table 5, effective October 1, 2026). In FY2026 it was 1.9370, a change of -0.7%.

What is the average length of stay for DRG 100?

CMS reports a geometric mean length of stay of 4.3 days and an arithmetic mean of 6.2 days for FY2027. The geometric mean is used for transfer-payment calculations.

Which DRGs are in the same CC/MCC family as 100?

DRG 101 (Seizures without MCC, weight 0.8950). The family's weights range from 0.8950 to 1.9240, so documented complications and comorbidities change payment materially.

What documentation supports the severity level of DRG 100?

DRG 100 requires at least one secondary diagnosis on the CMS Major Complication or Comorbidity list, documented as present and clinically addressed during the stay (monitored, evaluated, treated or extending the stay). Conditions such as acute respiratory failure, severe sepsis or acute kidney injury with specified cause qualify only when the attending's note states the diagnosis itself, not just the lab values. Recovery auditors downgrade this group to the CC or base level when the MCC rests on an unconfirmed query or a resolved historical condition, so the query response and the discharge summary must agree.

Which codes group to DRG 100?

The v44 Definitions Manual lists 62 principal diagnosis codes for this group. Examples from the principal diagnosis list: G40001 (Localization-related (focal) (partial) idiopathic epilepsy and epileptic syndromes with seizures of localized onset, not intractable, with status epilepticus); G40009 (Localization-related (focal) (partial) idiopathic epilepsy and epileptic syndromes with seizures of localized onset, not intractable, without status epilepticus); G40011 (Localization-related (focal) (partial) idiopathic epilepsy and epileptic syndromes with seizures of localized onset, intractable, with status epilepticus); G40019 (Localization-related (focal) (partial) idiopathic epilepsy and epileptic syndromes with seizures of localized onset, intractable, without status epilepticus).

Is DRG 100 a post-acute transfer DRG?

Yes. CMS flags DRG 100 under the post-acute care transfer policy, so a discharge to a qualifying post-acute setting before the geometric mean length of stay is paid a per-diem amount rather than the full DRG payment.

Sources

Every figure on this page is taken from the CMS publications below, as released by the Centers for Medicare & Medicaid Services. Projection built 2026-10-01. Verify against the primary file before billing or contracting decisions.

Disclaimer

This page is an operational reference compiled from the CMS IPPS FY2027 final rule (Table 5) and the v44 ICD-10 MS-DRG Definitions Manual. Relative weights are national factors; actual payment depends on each hospital's wage-adjusted base rate, add-ons, outliers and transfer adjustments. Nothing here is legal, clinical or billing advice; verify grouping against your encoder and the published CMS files.