Background: Diabetes mellitus is a glucose metabolic disorder which occurs when the body is unable to regulate blood glucose. High blood glucose level is toxic to body organs and leads to organ failure and death. Blood glucose levels are regulated through homeostatic process by glucagon and insulin hormones which act antagonistically. Objective: To determine saliva and blood glucose levels of patients attending Kenyatta University Teaching Research and Referral Hospital in Nairobi, Kenya. Material and Methods: A cross sectional correlational study was carried out with a sample size of 105 participants at the KUTRRH diabetic clinc. Sample size was tabulated from a table published by Karimollah Hajian-Tilaki and confidence interval set at 95% with a significance margin of error at 5%. Blood and saliva glucose levels were determined using Bs120 Mindray biochemistry auto analyzer. Raw data was entered in Microsoft Excel spread sheet and then exported to SPSS version 26.0 for statistical analysis. Result: The mean random saliva glucose levels of diabetic individuals was 0.367±0.040 mmol/l whereas the mean random saliva glucose of non-diabetic individuals was 0.023±0.002 mmol/l (p<0.001). The Pearson’s correlation coefficient between random saliva glucose and random blood glucose in diabetic and non-diabetics were r=0.65 and r= 0.51 respectively (p<0.001). Conclusion: Our study concluded that saliva specimen have a measurable level of glucose. The levels are different between diabetic and non-diabetic and therefore can be used in assay for screening and diagnosis of diabetes mellitus.