Final answer:
A provisional diagnosis of diabetes mellitus can be made through fasting glucose tests. A fasting glucose level higher than 125 mg/dL is indicative of diabetes.
Step-by-step explanation:
Diabetes mellitus can be diagnosed through various tests, including fasting glucose tests, glucose tolerance tests, and insulin tolerance tests. For a provisional diagnosis of diabetes mellitus, a fasting glucose level higher than 125 mg/dL is considered indicative of diabetes. Fasting glucose levels between 100 and 125 mg/dL are classified as pre-diabetes.