Volunteers take 50 g of glucose in 250 ml of water in 5 minutes.Then, they are tested blood glucose levels (taken from the fingertips) at 15, 30 ,45, 60, 90, and 120 minutes. There is 3 days for wash out period. These tests will be repeated for 3 times for baseline glucose calculation. After that, volunteers take 50 g of longan syrup in 250 ml of water in 5 minutes.Then, they are tested blood glucose levels (taken from the fingertips) at 15, 30 ,45, 60, 90, and 120 minutes. Glycemic index of longan syrup is calculated from area under the curved of blood glucose after longan syrup taking divided to mean of area under the curved of blood glucose after glucose taking.

Inclusion Criteria:

• Ages 18-60 years
• Never diagnosis as diabetes mellitus of thyroid dysfunction
• Fasting plasma glucose less than 100 mg/dl
• Body mass index 18.5-24.9 kg/m2
• Be willing to be subjects in this study

Exclusion Criteria:

• Know longan allergy or have history of adverse events from longan
• Take medicines, herbs, or food supplements including thiazide diuretics, beta-blockers ,and estrogen that have an effect on blood sugar level in 1 month before this study starting
• Severe comorbidity or uncontrolled diseases
• Pregnancy and lactation
• Participated in other studies