The mentolabial approach is a novel, safe, and effective method of blood collection in rats (Rattus norvegicus) and Chinese hamsters (Cricetulus griseus).

OBJECTIVE: To assess the safety, efficacy, and repeatability of a novel technique, mentolabial blood collection, in rats (Rattus norvegicus), Chinese hamsters (Cricetulus griseus), and long-tailed chinchillas (Chinchilla lanigera) and to characterize the associated anatomy through dissection and histopathology. METHODS: A prospective study was conducted in rats (n = 10), Chinese hamsters (10), and long-tailed chinchillas (12) from February 2026 to March 2026 to evaluate mentolabial blood collection. Animals were chemically restrained, and a needle was inserted through the skin below the inferior labium, targeting the gingival vein. Success was defined as a blood sample of ≥ 0.1 mL. A subset of Chinese hamsters (n = 6) underwent serial venipuncture, and hematology values were compared at days 0, 7, and 14. An additional 2 rats, 2 Chinese hamsters, and 1 long-tailed chinchilla were included for anatomical characterization. RESULTS: The success rate of the mentolabial approach was 100% (10 of 10) in rats and Chinese hamsters and 75% (9 of 12) in long-tailed chinchillas. No animals experienced clinical complications, and histopathology in rats and Chinese hamsters did not reveal adverse effects. In Chinese hamsters, hematologic parameters remained within reference range with no significant differences over time. CONCLUSIONS: Mentolabial blood collection is safe in sedated or anesthetized rats, Chinese hamsters, and long-tailed chinchillas and is highly effective in rats and Chinese hamsters, yielding clinically relevant blood volumes with precise control and minimal risks. CLINICAL RELEVANCE: The mentolabial approach may facilitate more routine bloodwork analysis in rodents by veterinarians and, in research settings, may improve animal welfare and contribute to refinement and reduction.