When your health check-up includes both a gastroscopy and a colonoscopy, it can feel a little daunting. For a lot of people, the hardest part isn't the procedure itself but the prep stage: "What am I not supposed to eat the night before? What do I do about my medications?" Honestly, once you walk through the steps, it isn't that complicated. The two exams look at different parts of the body, so the prep differs a bit, and since people often have them done together, it's easy to mix things up.
The gastroscopy is fairly simple. The evening before, eat lighter than usual and finish early, and then fast from around midnight on. The stomach needs to be empty so the lining shows up clearly; if there's still food in there, some areas get missed. It's also safer to stop drinking water a few hours before. If you choose a sedated (sleep) endoscopy, you may feel foggy and dizzy for a while afterward, so it's best to keep that day clear of driving or traveling far on your own.
The colonoscopy is the real hurdle. The whole point is "emptying the bowel," which means drinking the prescribed bowel prep solution on schedule, in split doses, with plenty of water. The taste is rough enough that you'll want to give up halfway through, but if the bowel isn't clean, small polyps or lesions can be hidden under stool and missed, and then you'd have to repeat the exam. Many people find it easier to chill the solution and drink it through a straw, with a lemon candy in their mouth to wash it down. When the last fluid that comes out is nearly clear and pale yellow, that's the sign you're well cleaned out.
There's also the diet to watch for a few days ahead. Starting 2-3 days before, avoid high-residue foods such as fruit with seeds, seaweed like kim and miyeok, multigrain rice, and tough seasoned greens, and stick to soft options like plain rice porridge or white rice, which makes emptying the bowel easier. The other must-check item is your medications. Blood thinners (anticoagulants and antiplatelet drugs), diabetes medications, and iron supplements may need to be adjusted a few days before the exam, so if you take anything regularly, mention it when you book so they can tell you whether to pause it or continue. Stopping on your own and just taking everything as usual are both risky.
On the day of the exam, wear comfortable clothes, and bring your glasses, dentures, or lenses in a way that's easy to remove. If you had sedation, have someone come with you or arrange for a person to pick you up afterward. If you had a biopsy or a polyp removed during the exam, it's best to skip spicy food and alcohol and rest that day, and if you keep passing black stool or have severe abdominal pain, don't tough it out: call right away.
To sum up: gastroscopy means fasting, colonoscopy means emptying the bowel plus adjusting your diet, and both call for a medication check. As long as you don't miss these three things, it usually goes smoothly. It looks fussy on paper, but once you've done it, it feels much lighter the next time. The exact prep varies a little from one clinic to the next, so go by the instructions you were given and what your medical team tells you.
This article is general health information and does not replace a diagnosis or treatment from a medical professional. Follow the specific guidance and instructions provided by the facility where you have your exam.