What started out as a storefront medical clinic founded by three college classmates has grown into a practice that serves more than 6,000 patients and has a budget of more than $1 million.

The North Side Christian Health Center is growing into a building more than double its size, 13 years after opening a storefront on East Ohio Street.

Renovation of the four-story, century-old building on Middle Street should be complete by August, said Floyd Cephas, the clinic's executive director.

In January, the clinic created a satellite office in Northview Heights and last month hired a new doctor, its first pediatrician.

Mr. Cephas calls the clinic "the little engine that could," chugging up the slope of rising health care costs and numbers of needy. Twenty percent of its patients have no medical insurance and 57 percent are clients of Medicare and Medicaid.

"The need is so great that sometimes, trying to address it, you feel as if the blood is draining out of your body," said Dr. J. Todd Wahrenberger, a founder and current medical director.

He was one of three friends who met as undergrads at Gannon University and founded the clinic together as young physicians.

They treated 900 patients the first year, 1995, with a nurse, a secretary, a volunteer accountant and fund-raiser. Now the 18-employee practice sees 6,500 patients, 1,100 visits a month. More than 60 percent of the patients are North Siders.

Of the three founders -- who included Dr. Dan Holt -- Dr. Wahrenberger and Dr. Mark Guy remain. Two full-time and three part-time doctors work with two physician's assistants.

As Christians, the friends wanted to practice medicine as a mission, Dr. Wahrenberger said. "You're supposed to do a foreign mission, but I remember thinking, 'but I like Pittsburgh.' "

In medical school, he trained with Dr. David Hall, founder of the East Liberty Family Health Care Center. Based on that model, no one is turned away. Patients without coverage pay what they can.

Altruism leaves a $30,000-$40,000 annual shortfall the organization has to cover, said Joseph Luciana, president of the board. The medical budget is now more than $1.2 million a year. "We have individual donors, a lot of churches, corporations and local foundations that support us."

Dr. Wahrenberger said 50 percent of the clinic's patients have mental health and emotional disorders, and addiction -- increasingly, abuse of legal drugs -- is a "huge problem."

About 15 percent of people who seek care have to be referred for specialized care, like surgery or cancer treatments. Without insurance, a patient facing six $5,000 chemotherapy treatments may qualify for some kind of aid, he said, "or we might call an oncologist and say, 'We've sent you five insured patients, now here's one with no insurance, and you're going to take him, aren't you?' "

Pediatrician Kate DeAntonis, formerly of Children's and Mercy hospitals, said she is "excited to be in a job where I can serve the under-served," she said. "I have always wanted to."

Pediatrics will have its own section in the new home, which UPMC sold to the nonprofit, donating $390,000 of the $644,000 cost in return for tax credits. The resulting $250,000 mortgage is being financed by the Northside Community Development Fund.

Mr. Cephas said he will seek green building certification for the renovation. It has heating coils in the floor, materials made with no emitting gases, energy-efficient windows and "a living roof" of plantings.

Mercy Behavioral Health, which has provided counseling at the clinic, will be able to expand its counseling and include treatments in the new site, which also has a kitchen for nutrition classes.

"We specialize in poverty medicine," said Dr. Wahrenberger, who works for 30 to 40 percent less than private family practice doctors make.

"We have found we can live on this, but to be competitive, we probably need to raise" our physicians' pay. "It's better than it used to be because our fund raising is better.

"But I think about this a lot: Five minutes in Iraq could fund this operation for 10 years."