Madam F. Kayes Bitters® is an herbal formulation commonly used in Nigeria and some African countries in the management of diabetes mellitus and other diseases conditions. This study evaluated the in-vivo hypoglycaemic activity, as well as acute toxicity of the polyherbal formulation to provide its efficacy and safety. Healthy albino mice (20-30 g) and Sprague Dawley female rats (90-130 g) were used for this study. Acute toxicity study (LD50) of the herbal formulation was determined by methods originally described by Miller and Tainter in 1994. Following oral dosing with glucose (2 g/kg) in normal fasted animals, herbal formulation (HF) at various doses was administered and blood glucose levels at 30 minutes, 60 minutes, 90 minutes, and 120 ...