WASHINGTON — Diabetics gained a new way of controlling their blood sugar levels Tuesday with federal approval of a novel pill for Type 2 diabetes, which affects about 20 million Americans.

The Food and Drug Administration said it approved Januvia, which enhances the body's own ability to lower blood sugar levels, after clinical trials showed the new pill works just as well as older diabetes drugs, but with fewer side effects like weight gain. The drug is made by Merck and Co.

Merck is expected to charge $4.86 for the once-daily tablet, a price tag that may limit its use. Older diabetes drugs can cost 50 cents a day.

Januvia, also known as sitagliptin phosphate, works with a one-two punch: It increases levels of a hormone that triggers the pancreas to produce more insulin to process blood sugar while simultaneously signaling the liver to quit making glucose. The pill does that by blocking production of an enzyme, called DPP-4, that normally inactivates that hormone.

Januvia is unlike any other oral drug for treating Type 2 diabetes. However, Novartis AG hopes to win FDA approval for a similar drug later this year.

"In the way the diabetes story is being played out, we are beginning to have agents that are allowing us to have some control over blood sugars without weight gain. That is the excitement about these products," said Dr. Stuart Weiss, an endocrinologist and assistant clinical professor at New York University School of Medicine.

In Type 2 diabetes, patients either don't produce enough insulin or cells in the body ignore it. Insulin is needed to process sugar. Without it, blood sugar levels soar.

The FDA approved Januvia for use in addition to diet and exercise to improve blood sugar levels in patients with Type 2 diabetes, alone or in combination with other commonly prescribed drugs.

"For the millions of Americans with Type 2 diabetes, who continue to have inadequate blood sugar control, the approval of Januvia marks an important advance in the fight against diabetes," said Dr. Steven Galson, director of FDA's Center for Drug Evaluation and Research. "We now have another new option that treats the disease in an entirely new way that can be added to existing treatment regimens to help patients gain more control over their blood sugar levels."

The most common side effects of Januvia in clinical studies were upper respiratory tract infection, sore throat and diarrhea, the FDA said.

Merck hopes to win FDA approval in late March for another pill, called MK-0431, that combines Januvia and the diabetes drug metformin.

"There is a huge need for additional therapeutic options in this marketplace," said Jay Galeota, who manages Merck's global diabetes drug business.

More than 230 million people worldwide have diabetes, up from just 30 million in 1985, according to the International Diabetes Federation.