Aims: Diabetes mellitus (DM) (Ziabetus Shakri) is a common metabolic disease affecting 150,000,000 people worldwide. Despite the recent advancements in management of Diabetes its relative co-morbidities and mortality is ever increasing globally. Unani scholars had claimed the effectiveness of several anti-diabetic drugs in the classical texts in the management of DM, but it lacks scientific documentation. Hence, a clinical trial was contemplated to evaluate the efficacy of test drug Tahlab (Spirulina) in patients of type 2 DM. Methods:The study was a single blind randomized standard control conducted on 40 patients of type 2 DM. 30 subjects were allocated to test and 10 to control group. Test group received 7 grams of Tahlab powder twice a day, and control group received Metformin (500 mg) 1 tablet twice a day for a period of 45 days. Subjective and objective parameters were assessed at 0, 15 th , 30 th , 45 th day. Results:The Mean score for FBS in test group has declined from 245.53 to 204.87 and PPBS from 345.73 to 303.67 respectively. The Mean score for FBS in control group has declined from 227.60 to 191.80 and PPBS from 329.60 to 282.80 respectively. Intergroup comparison revealed test drug to be similar to that of control drug in reducing FBS and PPBS. HbA1c and urine sugar remained unaltered in both groups. The results were assessed statistically using two tailed student t test, paired proportion test and Fischer exact test. Conclusions:The study revealed that the test drug is safe and equally effective when compared to control drug.