Introduction: Diabetes mellitus is a major cause of morbidity and mortality worldwide, with a prevalence of 347 million in 2013. Complementary and Alternative Medicines (CAM) are a group of remedies that is fast gaining acceptance among individuals. Cinnamon, Bitter gourd (Momordica charantia) and Fenugreek (Trigonella foenum-graecum) are 3 widely used CAMs used worldwide for the treatment of diabetes. Data on safety and efficacy is limited, but the consumption is wide. Crepe ginger (Costus speciosus) and Ivy gourd (Coccinia grandis) are 2 plants used widely in the Asian region for their presumed hypoglycaemic properties.

Objective: In this review, we analyzed the available evidence for the 5 CAMs mentioned above in terms of in-vitro studies, animal studies sand clinical trials. We also describe the mechanisms of hypoglycaemia and safety concerns where there is available evidence.

Results and conclusions: Clinical trials that studied the hypoglycaemic effects of Cinnamon, bitter gourd, fenugreek and ivy gourd showed conflicting results. Direct comparison between studies remains a challenge in view of the baseline heterogeneity of subjects, differences in substrate preparation, variable end points and poor trial design. Short durations of study and small number of subjects studied is universal. Crepe ginger has not been studied adequately in humans to draw conclusions.In view of the high prevalence of use and safety and efficacy issues, there is an urgent need to study their hypoglycaemic and adverse effects in well-designed long-term clinical trials.