Billing codes · ICD-10-CM code
N18 chronic kidney disease codes for renal nutrition claims
By Javier Alvarez · Updated · 4 min read
| Category | N18, Chronic kidney disease (CKD) |
|---|---|
| Billable | N18.1, N18.2, N18.30, N18.31, N18.32, N18.4, N18.5, N18.6, N18.9 |
| Not billable (headers) | N18, N18.3 |
| Code first | Diabetic CKD (E11.22 etc.) or hypertensive CKD (I12.-, I13.-) |
| Also add | Z94.0 kidney transplant status; Z99.2 dialysis status with N18.6 |
| Medicare MNT | Covered for renal disease not on maintenance dialysis, and 36 months post-transplant |
| FY2027 change | None to N18 (Oct 1, 2026) |
Renal nutrition is one of the few areas where Medicare covers dietitian visits directly, which makes the N18 codes worth getting exactly right. Most CKD claim problems come from three things: a stage 3 code with no a/b, CKD coded without the diabetes or hypertension that caused it, and a patient on dialysis billed under a benefit that excludes them.
N18 codes in plain English
| Code | Descriptor | Notes |
|---|---|---|
| N18.1 | CKD, stage 1 | |
| N18.2 | CKD, stage 2 (mild) | |
| N18.30 | CKD, stage 3 unspecified | Stage 3 without a/b documented |
| N18.31 | CKD, stage 3a | |
| N18.32 | CKD, stage 3b | |
| N18.4 | CKD, stage 4 (severe) | |
| N18.5 | CKD, stage 5 | Not ESRD unless the provider documents ESRD |
| N18.6 | End stage renal disease | Includes CKD requiring chronic dialysis; add Z99.2 for dialysis status |
| N18.9 | CKD, unspecified | Use only when the stage isn't documented |
N18 and N18.3 are headers. An N18.3 claim is rejected as an invalid code.
No N18 codes changed in the FY2027 update (October 1, 2026).
Choosing the right code
Section I.C.14.a of the Official Guidelines, and the tabular notes, give the rules:
- Stage from the provider. CKD severity is coded by stage. If both a stage and ESRD are documented, code N18.6 only.
- Diabetic CKD comes first. The N18 category says to code first any associated diabetic CKD (E08.22, E09.22, E10.22, E11.22, E13.22). ICD-10-CM's "with" convention presumes the link when both diabetes and CKD are documented, unless the provider says they're unrelated. So it's E11.22 + N18.x, not E11.9 + N18.x. See E11 type 2 diabetes codes.
- Hypertensive CKD comes first too. When hypertension and CKD are both present, assign I12 (hypertensive CKD) with the N18 code as secondary for the stage (Section I.C.9.a.2), unless the provider says the CKD isn't related to the hypertension. With heart disease, it's I13.
- Transplant. A patient with a kidney transplant can still have CKD. Assign the N18 stage and Z94.0 (kidney transplant status). CKD alone isn't a transplant complication.
- Don't stage from labs yourself. Your note can record the eGFR the patient's labs show. If it doesn't match the documented stage, ask the provider. Don't recode.
Coverage for renal MNT
Medicare covers MNT for beneficiaries with renal disease on referral from a physician (NCD 180.1; 42 CFR 410.130-410.132). The regulation defines renal disease as:
- Chronic renal insufficiency: reduced kidney function not severe enough to need dialysis or transplant, GFR 15-59 ml/min/1.73m²
- End-stage renal disease when dialysis is not received
- The 36 months after a kidney transplant
MNT for renal disease is not covered for beneficiaries on maintenance dialysis, which is paid under the ESRD benefit instead. For renal disease, as for diabetes, it's 3 hours the first year and 2 hours after. More hours are available after a new referral for a change in diagnosis, condition or treatment, billed with G0270/G0271.
The GFR range matters. Under standard KDIGO staging, 15-59 is roughly stages 3a through 4. A referral for stage 1 or 2 CKD alone (GFR 60 or above) may not meet Medicare's definition unless the patient also has diabetes. Put the qualifying diagnosis, and the referring physician's NPI, on the claim. Medicare MNT billing covers the referral in detail.
Commercial plans usually cover renal MNT under the medical benefit. Aetna's CPB 0049, for example, lists kidney disease among the chronic conditions where nutritional counseling is medically necessary. Visit limits and referral rules vary. The CKD niche itself is discussed in best nutrition niches for reimbursement.
Pairing with CPT codes and secondary codes
| Scenario | CPT | Diagnosis order (example) |
|---|---|---|
| Medicare, CKD 3b, no diabetes or HTN documented | 97802 × 4 | A: N18.32 |
| Medicare, diabetic CKD 3a | 97802 × 4 | A: E11.22, B: N18.31 |
| Hypertensive CKD stage 4 | 97803 × 2 | A: I12.9, B: N18.4 |
| Post-transplant (within 36 months), CKD 2 | 97803 × 3 | A: N18.2, B: Z94.0 |
| Extra hours after a new referral (diet change for rising potassium) | G0270 × units | A: E11.22, B: N18.4 |
All examples are made up. Point each service line at the code that establishes coverage.
What the note must show
- The provider's CKD diagnosis with stage, plus diabetes or hypertension if documented, from the referral or chart.
- For Medicare: the physician referral, the current year's hours used, and no maintenance dialysis.
- Relevant labs as reported (eGFR, potassium, phosphorus, albumin), your assessment and intervention.
- Time face to face for units.
Denials and fixes
| What you'll see | Likely cause | Fix |
|---|---|---|
| Rejected: invalid diagnosis | N18.3 or N18 billed | N18.30/N18.31/N18.32 |
| CO-16 (Medicare) | Missing referring physician NPI | Add it and resubmit |
| CO-167 / CO-50 | Stage 1-2 only, no qualifying diagnosis for Medicare | Check the referral for diabetes or a qualifying stage |
| Denied as not covered for dialysis patients | Patient on maintenance dialysis | Not billable under MNT; nutrition care for dialysis patients usually comes from the dialysis facility's dietitian |
| CO-119 | Annual hours used | New referral for a change → G0270; otherwise wait for the next year |
A referral that's missing something is behind many of these. Physician referrals for dietitians lists what a complete one includes.
For the other diagnosis codes on nutrition claims, see the ICD-10 codes for dietitians reference.