A ‘Low Renal Toxicity’ Cannabis Paper Still Reported Higher-Dose Kidney Changes

forensic toxicology working group members October 28, 2026 Forensic Toxicology

A preliminary rat study reported kidney-tissue changes at its higher cannabinoid doses despite a title emphasizing low renal toxicity. The same study did not measure kidney function, so neither blanket reassurance nor a diagnosis of renal failure follows from its findings.

What the rats received

Forty male Wistar rats were allocated to five groups, including vehicle, CBD and CBD/THC nanoemulsions at two dose levels. Oral treatment continued daily for 21 days. Investigators examined kidney histology and immunohistochemical markers.

The lower and higher labels refer to the doses within this experiment. They do not establish low or high exposure categories for human users.

Positive and null tissue findings

Higher-dose groups showed structural abnormalities, including tubular and glomerular changes, together with increased Ki-67 and cleaved caspase-3 staining. GST-P increased significantly only in the higher-dose CBD group. The lower-dose groups did not show significant changes on the assessed endpoints.

Ki-67 reflects cell-cycle activity; it cannot independently distinguish repair from pathological proliferation. The findings therefore should not be converted into a cancer claim.

The missing functional evidence

The authors explicitly stated that serum creatinine, urea and urinary functional biomarkers were not assessed. Morphological abnormalities can be important, but they do not directly quantify filtration or establish clinical renal dysfunction.

The vehicle control helps interpret the preparation, while formulation–drug interactions remain possible. A short, small animal experiment cannot determine long-term human kidney safety or a safe consumer dose. The proper conclusion retains both the higher-dose tissue signal and the absence of direct functional measurements.