# Albuminuria, UACR, and the Expanded Teaching Heat Map

Andrew Bland, MD, FACP, FAAP · October 19, 2026

Albuminuria adds information about kidney injury and risk that eGFR alone cannot provide. Most albumin remains in the circulation; glomerular pressure, barrier integrity, and proximal tubular handling influence how much appears in urine.

![Diagram](https://urinenephrology.org/2025_UDPA_Lectures_Live/assets/albuminuria-uacr-bland-a4-2026-10-19.png)

Urine albumin (mg/L) / urine creatinine (g/L) = UACR (mg/g). UACR is not total urine protein.

| Teaching label | UACR (mg/g) | Standard KDIGO category |
| --- | --- | --- |
| A1 | <30 | A1 |
| A2 | 30–300 | A2 |
| A3: lower range | >300 to 1,000 | A3 |
| A3: higher range | >1,000 to 3,000 | A3 |
| “A4”: teaching label | >3,000 | A3 |

The scorecard-inspired teaching extension separates the broad A3 band into three buckets. The upper boundary belongs to the preceding bucket: 1,000 is in the lower A3 range, 3,000 is in the higher A3 range, and values above 3,000 enter the teaching “A4” bucket. “A4” is not an official KDIGO category; all three buckets remain KDIGO A3.

The expanded heat map retains KDIGO risk colors within A3; it does not assign additional validated risk classes or individual percentages. Interpret UACR with GFR, sediment, clinical context, and persistence.

## Sources

- [NIDDK: assessment of urine albumin](https://www.niddk.nih.gov/health-information/professionals/clinical-tools-patient-management/kidney-disease/identify-manage-patients/evaluate-ckd/assess-urine-albumin)
- [KDIGO 2024 CKD guideline](https://kdigo.org/wp-content/uploads/2024/03/KDIGO-2024-CKD-Guideline.pdf)
- [KDIGO digital heat map](https://kdigo.org/heat-map/)

[Open the interactive heat map](https://urinenephrology.org/2025_UDPA_Lectures_Live/case-based-lectures/opening-lecture.html#ckd)

## Historical A4 context

The Canadian Society of Nephrology’s 2015 AJKD commentary proposed A4 for nephrotic-range albuminuria (ACR >2,220 mg/g). AJKD is the NKF journal. This lecture uses >3,000 mg/g for its teaching A4; current KDIGO remains A1–A3.

[CSN commentary, AJKD 2015](https://pubmed.ncbi.nlm.nih.gov/25511161/)