Under what circumstances is it recommended NOT to certify a driver with diabetes mellitus?

A recommendation against certifying a driver with diabetes mellitus is primarily based on the risk of severe hypoglycemic reactions. If a driver has experienced a severe hypoglycemic episode in the last 12 months, it indicates that their condition may not be well managed, posing a serious risk not only to their own safety but also to the safety of others on the road. Severe hypoglycemia can lead to loss of consciousness or impaired cognitive function, increasing the likelihood of accidents and dangerous situations.

In terms of contextualizing the other options, while mild hypertension can be a concern, it is generally not as critical as managing diabetes effectively, especially if hypertension is under control. Age alone, such as being over 60, does not inherently make a driver unfit, as many older individuals operate vehicles safely with properly managed health conditions. Recent changes in medication may suggest instability in a driver's condition but do not automatically disqualify them unless these changes lead to severe management issues like hypoglycemia. Thus, the most definitive indicator of fitness for duty in this scenario is a history of severe hypoglycemic reactions.