Katy Folven never leaves home without her insulin pen, but the busy Boston social worker sometimes forgets to track her daily doses.

When that happens, she must prick one of her already-calloused fingertips to measure blood sugar. That can mean as many as 10 punctures in a day.

Eli Lilly and Co. is introducing a unique insulin pen Thursday that could prevent some punctures. The Indianapolis drug maker's Memoir pen, the first on the market with a memory device, is for use with its top-selling insulin, Humalog.

The battery-operated pen, called the "Lexus" of insulin pens by one doctor, uses a computer chip to remember the last 16 insulin doses delivered.

Lilly says Memoir could reduce hassles for some of the 21 million Americans who live with diabetes, but others question whether it will catch on.

"The concept is beautiful," said Dr. William Hsu of the Joslin Diabetes Center, also in Boston. "Now the issue is, is it practical?"

Some predict U.S. insurers and patients might be hesitant to pay $100 for the pen and a separate fee for the insulin cartridges.

And while insulin pens are popular in Europe and Asia, only about 800,000 of the 4 million U.S. diabetics who need daily insulin injections use a pen. Most use syringes and insulin vials.

Matt Beebe, the company's U.S. brand team leader for Humalog, predicts that will change once Memoir enters the market. He said Lilly is debuting Memoir in the U.S. and may branch into Europe and Asia.

Hsu said the pen's price will keep him from prescribing it.

"I think it's expensive," he said.

Lilly plans to offer coupons that let patients buy one of the new pens for $45.

"Patients helped us develop it and gave us the idea to bring it to market, and we want to make sure they have access to it," Beebe said.

The new pen could boost Lilly's diabetes product portfolio, which took a hit last month when the company announced it was halting the construction of a Virginia insulin plant. Company officials have said they expect worldwide demand for Lilly's insulin products to grow, but not at levels projected when plans for the site were developed in 2003.

Lilly's diabetes portfolio accounted for nearly one-fifth of the company's $15.7 billion revenue in 2006, and analysts have predicted that figure could double in the next four years.

Lilly spent seven years developing the pen in partnership with Battelle Medical Device Solutions of Columbus, Ohio. It is one of three that Lilly plans to introduce this year, part of a strategy to increase Humalog demand, said Lehman Brothers analyst Tony Butler.

Memoir answers a call for more patient-friendly products, said Miller Tabak and Co. analyst Les Funtleyder. But he doubts it will lead to a noticeable revenue increase for the drug maker.

"That could change if everybody says they have to have it, like the next Tickle Me Elmo," he said. But he said the pen was "a step in the right direction for Lilly, and it certainly is where the world is going."

Folven, who was diagnosed with diabetes more than 20 years ago, said she plans to ask her doctor about Memoir.

"Having a backup is nice because it's not always easy when life gets going," she said.