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So, I have to do a colonoscopy soon, and my doctor prescribed PEG-3350/kcl SOD Lemon-Lime 4000ml for the prep. I've heard it's not the most pleasant experience, but I'm curious if anyone has tips or horror stories to share. What are the worst side effects you've experienced and how did you deal with it?

Also, does anyone know if the flavor is as bad as it sounds? And how long did it take for your stool to be clear? I've been reading about it, and some people have said they had to drink the entire 4L while others had an easier time. I'm hoping I get lucky with it. Here are some side effects to look out for:

Urgent Side Effects: See a doctor immediately

If you feel a rash, hives or start wheezing it might indicate an allergic reaction. Watch out for signs of kidney problems, such as inability to pass urine, blood in the urine, or sudden weight gain. A severe headache, vomiting blood, black or bloody stools, or rectal bleeding are all signs to get urgent medical help.

Some other serious side effects to look out for are dizziness, fatigue, mood changes, confusion, and decreased appetite

1 min read
last active 4/17/2026
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Comments (5)

J
justin_vargas4/15/2026

I had this prep for my colonoscopy last year. Make sure to follow the instructions to the letter and don't try to rush it. Drink plenty of clear liquids throughout the day, and try to stay hydrated. Oh, and don't plan on leaving the house much. Trust me on that one.

E
ethan_ferguson4/15/2026

I was surprised by how effective this was, but yeah the side effects were not pleasant, I definitely had some dehydration and electrolyte imbalances, symptoms include dizziness, fatigue, mood changes, confusion, and decreased appetite. I had to take it slow and steady, and I ended up having to go to the bathroom more often than I thought was humanly possible, but it does work

M
matthew_dixon4/15/2026

Drink it cold and have a trash can handy. You will need it. I had to take breaks every 20 minutes to rest. Protip: Don't try it on an empty stomach. I just want to power through the whole thing to get it over with, but this is not the day to challenge yourself

P
peter_tucker4/15/2026

I had a colonoscopy last week and used this prep. It wasn't fun, but it was worth it to make sure everything went smoothly during the procedure. I didn't have any major side effects, just some mild cramping and nausea. Oh and the taste, don't get me started. It's like drinking liquid soap. The lemon lime flavor didn't even come close to masking the taste. Just be prepared for the worst and hope for the best. You can do this!

J
joan_kim4/15/2026

I didn't have any issues with this prep, but my husband did. He had severe stomach cramps and had to take it slow. Just be prepared for the worst and hope for the best. And if all else fails, you can always throw it up and start again. But seriously, don't do that. It's gross and wasteful.