Diabetes mellitus is a major health challenge that has harmful effects on the quality of life globally as a result of its numerous complications. This study aimed to evaluate the positive modulatory effect of Lawsonia inermis (LI) Linn on various haemobiochemical parameters and lipid profiles in streptozotocin-induced diabetic rats. Ten groups of diabetic rats (n = 5) were orally administered 50 and 100 mg/kg of three different fractions of Lawsonia inermis: metformin (500 mg/kg) and glibenclamide (5 mg/kg), whereas untreated hyperglycaemic and normoglycaemic rats received distilled water. The results showed increased red blood cells (RBC) in treated rats compared to untreated diabetic rats. Hb, MCV, MCH, and MCHC decreased nonsignificantly, whereas WBC increased nonsignificantly. Neutrophil increased non-significantly in diabetic, untreated rats, while all the treatment groups decreased non-significantly. Lymphocytes and monocytes increased non-significantly (p > 0.05). Most treatment groups showed a non-significant (p > 0.05) increase in the platelet count. The ALT levels decreased non-significantly (p > 0.05) compared to normoglycemic rats. The AST levels decreased significantly (p < 0.01). ALP decreased non-significantly in both treated and untreated groups, whereas bilirubin did not show any significant changes. Creatinine and urea levels in untreated diabetic rats increased non-significantly, while treatment groups decreased non-significantly. Lawsonia inermis-treated rats showed significant improvement in erythrocytic fragility, while glycated haemoglobin in untreated-diabetic and glibenclamide-treated rats increased significantly (p > 0.001). Triglycerides and high-density lipoprotein decreased non-significantly, while low-density lipoprotein increased non-significantly (p > 0.05) in diabetic untreated rats. All treatment groups showed a non-significant (P > 0.05) decrease in low-density lipoprotein. Lawsonia inermis showed a significant positive modulatory effect on the haemobiochemical changes, glycated Hb, osmotic fragility, and lipid profile in streptozotocin-induced diabetic rats.