Heck, check right now. This is one of those things few people ask about until they need it, and then it might be too late. If you are not covered for medical care while traveling, we highly recommend purchasing trip insurance with medical coverage.
Note that Medicare does not cover most medical costs incurred outside the United States, so seniors especially should look into travel insurance before going abroad.
If you are traveling within your home country, the best way to find care covered by your insurance is to call your insurance company or visit its website. You can also check sites like HealthGrades.com for reviews of local doctors.
START MEDICATIONS RIGHT AWAY.
Many of us are reluctant to run to the nearest doctor or pharmacy when we're not feeling well, instead preferring to gut it out while a malady runs its due course.
When traveling, however, taking this tack might mean that your vacation is over by the time you actually feel better, so I encourage you to pounce on whatever medications are available as soon as you start feeling under the weather.
PROTECT YOUR TRAVELING COMPANIONS.
If one sick traveler is a source of misery for everyone on the trip, multiple sick travelers can shut things don't completely. If you feel an illness coming on, take immediate action to protect your fellow travelers.
Most common travel maladies last about a day or two -- or at least the worst of it lasts that long. If you employ some of the strategies above, get a ton of rest and wait it out for 18 to 36 hours, in most cases you can get fully back into the thick of your trip.
CODDLE YOUR DIGESTIVE SYSTEM.
You'll likely want to ditch any adventurous eating habits until you are well again; give your system the nutrients it needs, but don't tax it unnecessarily with risky or challenging foods.
Also, drinking plenty of water is a given, although it is important to make sure it is clean and safe (as contaminated drinking water may have been the source of your malady in the first place).