WAITING A WEEK TO

see his doctor for a sore throat isn't Dan Maffetone's idea of proper health care. Neither is waiting for hours in the emergency room and paying hefty co-insurance fees, especially given that he's responsible for 10% of all emergency room costs.

So for the past six years, every time a minor ailment like a cold, rash or upset stomach strikes, the 58-year-old investment advisor from Long Island, N.Y., heads to a nearby walk-in clinic where he sees a doctor within half an hour. It's not only fast and convenient, but with a $15 co-pay, it's inexpensive as well. "It's kind of a first line of defense," Maffetone says. "If you have something, you want a doctor to look at it and make sure it isn't something serious to be looked at further by your [regular] doctor."

Walk-in clinics, also called retail health clinics, can be found in places like strip malls, megastores and drugstores. They've been around for years, but didn't start proliferating until early 2006 when corporations like CVS, Walgreens, Target and Wal-Mart got into the business. By the end of 2007, there were 921 walk-in health clinics nationwide, compared with just 129 at the start of 2006, according to Merchant Medicine, an industry consultancy. Within the next five years, the number is expected to soar to 3,000.

For more on this, read 10 Things Your Primary-Care Physician Won't Tell You

"The genesis of [walk-in clinics' popularity] is the desire of the consumer for faster, cheaper and more accessible primary care," says David Chin, lead partner for PricewaterhouseCooper's Healthcare Research Institute, which in a recent report distinguished retail health clinics as one of the top eight health-care trends for 2008.

Some doctors are taking note. Dr. Jim King, president of the American Academy of Family Physicians, says his practice has developed a fast-track program that allows patients with a problem they would typically treat at a walk-in clinic (say, a sinus infection) to see a doctor on the same day and within 30 or 40 minutes of coming in. He has also extended his hours from 7:30 a.m. to 7:00 p.m. and keeps several appointment times open so patients who call with a cold or other emergency can be seen that same day. "It's a way to compete [with walk-in clinics]," he explains. "I know several practices are looking at doing things like that to improve the convenience for our patients and become patient-centered."

Until that day arrives, a walk-in clinic may be a good place to go for small health issues like a common cold or a stomach bug. However, before you go, be aware that these clinics come with limitations and potential drawbacks.

1. The menu is scarce

Walk-in clinics can treat a limited number of conditions, often regulated tightly by state-determined standards. "Most of these clinics are set up to take care of minor medical problems, such as colds, sore throats and respiratory-type illnesses," says King. The clinics don't do any lab work or X-rays, so if you walk in with a more serious or chronic condition, you may be turned away and referred to a physician anyway. (Regulations vary by state. Check with your state's department of health for specifics.)

2. The doctor isn't always in

When you walk into a clinic, chances are you won't be seen by a doctor. Most clinics are managed by nurse practitioners or physician's assistants and don't have a doctor present at all. This helps the clinics keep down costs in turn translating into lower bills for consumers but it may mean the personnel lacks the training or expertise to diagnose your condition. (Some states, such as California, require that drugstore health clinics have at least one supervising physician.)

Not that you're guaranteed to see a physician if you go to your regular doctor's office, anyway. According to the Massachusetts Medical Society survey, 41% of the state's residents had a medical appointment in which they saw a nurse in 2007. More than a third of those patients (35%) did so because they couldn't get an appointment with a doctor.

3. What happens there stays there

If you have a chronic condition, such as hypertension, asthma, or diabetes, watch out: Clinics don't have your medical records and typically don't share the information about your visit including the medications prescribed with your doctor unless you specifically request it.

This can be downright dangerous. "A medication could be prescribed that conflicts with something [the patient] is taking if they don't communicate that information," says Dr. Bruce Auerbach, an emergency practitioner and president-elect of the Massachusetts Medical Society.

Continuity of care is the main reason why the American Academy of Pediatrics discourages parents from taking their children to walk-in clinics, says Dr. Robert Corwin, a pediatrician in Rochester, NY and Chair of the Immunization Advisory Council of the State of New York. Even if a child has a minor condition, pediatricians may use those visits as a platform to discuss other health-care issues, such as catching your child up on immunizations or identifying undetected illnesses, he says.

4. Prescriptions mean profits

Eric Nixon, a sales rep in Winston-Salem, N.C., used to frequent walk-in clinics several years ago, when he didn't have health insurance. Convenience and fast access aside, he was pleased with the prescriptions: Much more often than "regular" doctors, he would get a strong antibiotic "that would take care of just about anything," he explains. Meanwhile, his family MD, he says, would start with a low dose and tell him to come back if he had further problems.

The clinic's prescription may sound like a cost-saver, but readily dispensing strong antibiotics can be dangerous, says Auerbach. (We've all heard of the super-bug.) It could also make even more money for the companies that own the clinic, since you're likely to fill that prescription at their pharmacy. "There's the concern that the entity that is making the recommendation for the patient to purchase something is also the entity that is selling the product," he says. "So there's a potential conflict of interest there."