In major cities, you'll have little cause for worry. Water is generally fine to drink, though cautious travelers may want to stick to bottled water. The problem you're most likely to encounter is traveler's diarrhea, from inexpensive food. Use common sense -- avoid eating unpeeled fruits and vegetables from street vendors, wash your hands frequently, and when trying a new fruit or vegetable, don't overdo it. Remember to wear sunscreen at all times, even in cool cities like Bogotá. You're closer to the sun, and you don't want to let sunburn ruin your vacation. In major cities, health care is adequate and professional, as long as you stick to private clinics. Public clinics tend to have long lines and are usually understaffed and underfunded.
If you are visiting the Andean region, altitude sickness is a possibility. Though it generally goes away after 2 to 5 days, it may be helpful to bring along Tylenol, Advil, or another over-the-counter painkiller. Symptoms include headache, shortness of breath, fatigue, nausea, and sleepiness. Try to take it easy the first day or two to avoid worsening your condition. You might experience altitude sickness in Bogotá or Tunja, or when hiking in the high Andes.
Though no vaccines are required to enter Colombia, it's a good idea to consider getting vaccinations for hepatitis A and B, typhoid, and yellow fever if you will be visiting the Atlantic or Pacific coasts, the Amazon region, or any other tropical region. (As a general rule, the more rural your location in the country's tropical regions, the higher your risk of contracting diseases such as malaria, yellow fever, or cholera). Dengue fever is another concern in the tropics, though unfortunately there is no preventative vaccine. You should also consider taking malaria pills if you will be visiting any of the above regions.
Note: This information was accurate when it was published, but can change without notice. Please be sure to confirm all rates and details directly with the companies in question before planning your trip.