With the government’s blessing, a drug giant is about to expand the market for its blockbuster cholesterol medication Crestor to a new category of customers: as a preventive measure for millions of people who do not have cholesterol problems.

Some medical experts question whether this is a healthy move.

They point to mounting concern that cholesterol medications — known as statins and already the most widely prescribed drugs in the United States — may not be as safe a preventive medicine as previously believed for people who are at low risk of heart attacks or strokes.

Statins have been credited with saving thousands of lives every year with relatively few side effects, and some medical experts endorse the drug’s broader use. But for healthy people who would take statins largely as prevention — which would be the case for the new category of Crestor patients — other experts suggest the benefits may not outweigh any side effects.

Among the risks raising new concerns, recently published evidence indicates that statins could raise a person’s risk of developing Type 2 diabetes by 9 percent.