Would you consider using an online coupon site—like Groupon or LivingSocial—to pay for medical care for you or an elderly loved one?

It may seem like an odd question, but many deal-a-day companies cite health care services as one of their rapidly growing offerings categories. Discounts on things like flu shots, eye exams, and dental care are becoming rapidly becoming commonplace on such sites.

Filling the cavities in coverage

For the cash-strapped caregiver there are definite benefits to using daily deal sites to help foot a few medical expenses. 50% off an eye exam and a free pair of glasses is certainly appealing—especially when some insurance programs don't cover everything a senior needs.

For example, neither Medicare nor Medicaid offers substantial dental or vision care coverage for elderly adults.

According to the Centers for Medicare and Medicaid Services website, things like dental care, hearing aids, and eyeglasses are usually not paid for because of the regulations that govern the parameters of coverage. However, there are certain types of Medicare Advantage plans that offer dental and vision benefits, but what is covered will vary depending on which plan a senior has.

Dental care does not come cheap. A regular check-up can cost anywhere from $75 to over $200, depending on whether a dentist does X-rays or not. This doesn't even take into account the cost of the dentures, implants, and extractions that many seniors need as they age.

Dental discounts are among the more common health-related offerings on deal-a-day sites. Usually the coupon only applies to a cleaning and X-rays, limiting its usefulness to seniors.

Other popular coupons include discounted eye exams. A recent Groupon offered an eye exam, and contact-lens or eyeglass package at up to 72% off the original price. There are stipulations of course, the deal only applies to certain brands of contacts and eyeglass frames and must be used within several months of purchase.

Exercise caution

It's easy to be sucked into an ad's hype, or dazzled by a hefty discount.

There's no denying that online coupons can help caregivers and their elderly loved ones save on care services that may not be covered by their insurance. But, experts advise caution when using deal-a-day sites.

Robert Stall, M.D., geriatrician, and owner of Stall Geriatrics, says that that if you see a good deal you should, "go for it, but go into it with due diligence." A caregiver needs to do their research and consult with a primary care physician if they are unsure about a particular service.

None of Stall's patients or their caregivers has ever consulted with him about a health care service coupon, but he encourages them to come to him with questions about such things.

Why you won't see general practitioners offering deals

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Even though discounts on health care are appearing more often on coupon sites, it's unlikely that you will ever see a seniors' primary care physician offering their services on one, because—in most cases—it's against the law for them to do so.

Doctors who accept Medicare patients are not allowed to accept discounts and must bill their patients the full co-pay required by their plan, says Stall. Most HMOs also have this requirement.

Remember, it's just good business

Stall urges caregivers and seniors to remember that deal-a-day coupon sites are marketing tools that some medical practitioners use to generate business.

Coupons are—in their purest form—advertisements that should be taken with the same grain of salt that would be applied to a television or newspaper ad.

Most deal-a-day sites allow a minimum of "ad-speak" on their coupons, but, according to Stall, people should be wary of any service that hawks a miracle cure, or hints that a competitor of theirs is somehow deficient.

Ultimately, Stall says "when it comes to your health, word of mouth is the best advertising."