A report by Avalere Health, a Washington-based advisory firm and consultant to the health care industry said seven of the ten most popular prescription drug plans chosen by seniors have double-digit percentage increases in their monthly premiums.

Senior citizens may have to start searching now for a better Medicare prescription plan

The Avalere report is in contrast to the Obama administration's report in August that announced the average premium for basic prescription drug coverage will stay the same in 2013 at about $30 a month. Here's a link to that announcement. At that time, U.S. Secretary of Health and Human Services Kathleen Sebelius said premiums were "holding steady."

For example, Humana Walmart's Preferred Rx Plan raised its premium by 23 percent. The plan, described by Avalere as "popular" and "low-cost", raised premiums to $18.50 for 2013.

The administration, through a spokesman at the Centers for Medicare & Medicaid Services, told the Associated Press that it did not dispute the Avalere estimates. But Brian Cook, Medicare spokesman, told AP that government health officials "continue to encourage seniors to shop around and find the plan that works best for them."

Avalere analysts seemed to agree, saying seniors should be particularly wary of new entrants to the market that may offer low-cost plans initially to gain market share initially but may be forced to raise premiums later depending on market conditions. Average premium increases for plans currently offering drug plans raised premiums 6 percent on average from this year to 2013, Avalere Health said.

In 2013, for example, UnitedHealth's new Medicare Rx Saver Plus plan is averaging $15 a month, Avalere said.  Analysts say insurance companies can offer low-cost plans but seniors need to be careful and ensure their pharmacy is in the health plans network.

Pharmacies are negotiating stricter arrangements with health plans that limit consumer choices through smaller networks of drugstores the benefits companies deem lower cost.

"Seniors need to carefully assess their options going into this open season to ensure that they have a plan that meets their needs," said Bonnie Washington, senior vice president of Avalere Health.

The annual open enrollment period when seniors can choose a drug plan or switch from one coverage to another begins Oct. 15 and runs to Dec. 7