Federal regulators on Tuesday approved a new class of oral drugs for Type 2 diabetes that are as effective as most existing treatments and avoid common side effects, such as dangerously low blood sugar.

The Food and Drug Administration said that Merck & Co.’s Januvia, a once-daily tablet, could be taken alone or in combination with the commonly used oral diabetes medicines metformin, Actos and Avandia.

Dr. Robert Meyer of the FDA’s Office of Drug Evaluation called Januvia a “useful addition” to the treatment arsenal.

“Not everybody optimally responds to each medication, or not everybody can tolerate each medication,” he said at a news conference. “Having a new drug in a new class for such a widely prevalent disease is important.”

But Dr. John Buse, director of the diabetes center at the University of North Carolina School of Medicine and president-elect of the American Diabetes Assn., said it was still uncertain how valuable the drug would prove to be.

Some commonly used older drugs “are very effective and are ridiculously cheap,” said Buse, who has consulted for many pharmaceutical companies. “The only sin they committed was becoming generic” and losing corporate marketing support.

Januvia will cost $4.86 a day, adding about $1,800 to the annual cost of treatment.

The drug is among several medicines recently approved for Type 2 diabetes, an illness linked to obesity that is reaching epidemic proportions worldwide and affects 20 million people in the U.S.

Galvus, a Norvatis drug similar to Januvia, is expected to receive FDA approval next month.