# CT with contrast and metformin **URL:** \ **Category:** Factual Questions\ **Created:** [November 5, 2021, 2:10am UTC](https://boards.straightdope.com/t/ct-with-contrast-and-metformin/953820 "2021-11-05T02:10:01Z")\ **Posts on this page:** 17\ **Page:** 1
**Author:** ![susan](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/susan/32/17537_2.png) [@susan](https://boards.straightdope.com/u/susan)\ **Post date:** [November 5, 2021, 2:10am UTC](https://boards.straightdope.com/t/ct-with-contrast-and-metformin/953820/1 "2021-11-05T02:10:01Z")
Factual question, not a request for medical advice. I have a CT with contrast tomorrow. The barium drink, while far from delicious, wasn’t as bad a colonoscopy prep (and was nothing like "drinking latex paint, which I had read online). Question: The consent form asks if I take metformin. In what way does metformin matter or affect the imaging? Thanks. ---
**Author:** ![Stranger\_On\_A\_Train](https://avatars.discourse-cdn.com/v4/letter/s/13edae/32.png) [@Stranger\_On\_A\_Train](https://boards.straightdope.com/u/Stranger_On_A_Train)\ **Post date:** [November 5, 2021, 2:13am UTC](https://boards.straightdope.com/t/ct-with-contrast-and-metformin/953820/2 "2021-11-05T02:13:24Z")
> **[Metformin and intravenous contrast](https://www.ncbi.nlm.nih.gov/pmc/articles/PMC3537815/)** Stranger ---
**Author:** ![Dr\_Paprika](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/dr_paprika/32/3042_2.png) [@Dr\_Paprika](https://boards.straightdope.com/u/Dr_Paprika)\ **Post date:** [November 5, 2021, 2:43am UTC](https://boards.straightdope.com/t/ct-with-contrast-and-metformin/953820/3 "2021-11-05T02:43:14Z")
Radiologists are very aware contrast agents can occasionally cause problems, especially in the kidney. Blood tests are generally available and doctors look at the patient’s age and creatinine to calculate the clearance to see how well the kidneys are working. Emergency doctors often wish to order abdominal CTs in patients who may need surgery or have suffered trauma. Contrast is helpful in many cases. The radiologists are sometimes reluctant and request patients with questionable renal function to be well hydrated with fluids or even to be started on medicines like GlcNac which are helpful. Metformin use may signify diabetes which also can cause kidney concerns. However, metformin also is not generally prescribed if kidney function is pretty bad. At best, the survey would remind the radiologists to look at the bloodwork and see if it is advisable to add hydration and medicines like GlcNac. ---
**Author:** ![nearwildheaven](https://avatars.discourse-cdn.com/v4/letter/n/90db22/32.png) [@nearwildheaven](https://boards.straightdope.com/u/nearwildheaven)\ **Post date:** [November 5, 2021, 4:28am UTC](https://boards.straightdope.com/t/ct-with-contrast-and-metformin/953820/4 "2021-11-05T04:28:31Z")
Metformin use can increase the risk of lactic acidosis if taken within 48 hours of some IV contrast media. > **[Metformin and contrast media: where is the conflict? - PubMed](https://pubmed.ncbi.nlm.nih.gov/9640281/)** > > Intravascular administration of iodinated contrast media to patients who are receiving metformin, an oral antidiabetic agent, can result in lactic acidosis. However, this rare complication occurs only if the contrast medium causes renal failure, and... ---
**Author:** ![Keeve](https://avatars.discourse-cdn.com/v4/letter/k/f07891/32.png) [@Keeve](https://boards.straightdope.com/u/Keeve)\ **Post date:** [November 5, 2021, 9:52am UTC](https://boards.straightdope.com/t/ct-with-contrast-and-metformin/953820/5 "2021-11-05T09:52:22Z")
If I’m understanding the responses correctly, the problem is NOT that metformin makes it hard to read the CT scan, but rather that (in some cases) the metformin doesn’t play nicely with the contrast stuff and can cause kidney problems. Accurate oversimplification? ---
**Author:** ![Dr\_Paprika](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/dr_paprika/32/3042_2.png) [@Dr\_Paprika](https://boards.straightdope.com/u/Dr_Paprika)\ **Post date:** [November 5, 2021, 5:18pm UTC](https://boards.straightdope.com/t/ct-with-contrast-and-metformin/953820/6 "2021-11-05T17:18:33Z")
Very few medicines would even show up on a CT scan. You have it right. To paraphrase, radiation and contrast are used because they are generally safe in small doses and the benefits outweigh the risks. But there are risks. A small percentage of people who receive contrast, similar to people who take anti-inflammatories, find it stresses their kidneys. This effect is usually mild if it occurs. But radiologists take the risk seriously. It is more likely to happen to diabetics, and metformin itself seems to increase the risk a little as well. Risk can be lessened by being well hydrated, missing a few doses and by other antidotes if necessary. Still, try to limit how many CTs you get (especially if prone to kidney stones). ---
**Author:** ![Marvin\_the\_Martian](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/marvin_the_martian/32/2898_2.png) [@Marvin\_the\_Martian](https://boards.straightdope.com/u/Marvin_the_Martian)\ **Post date:** [November 5, 2021, 6:13pm UTC](https://boards.straightdope.com/t/ct-with-contrast-and-metformin/953820/7 "2021-11-05T18:13:07Z")
When I had a CT the tech said that once they inject the contrast I’d probably feel like I’m wetting my pants (even though I’m not). That’s exactly how it felt. Is that related to the kidney stress issue? Or a completely unrelated phenomenon? ---
**Author:** ![susan](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/susan/32/17537_2.png) [@susan](https://boards.straightdope.com/u/susan)\ **Post date:** [November 5, 2021, 6:52pm UTC](https://boards.straightdope.com/t/ct-with-contrast-and-metformin/953820/8 "2021-11-05T18:52:03Z")
Thanks, all! It’s very interesting. FWIW, my kidney function is fine and no one directed me to discontinue metformin–they just wanted to now about it on the consent form. ---
**Author:** ![aruvqan](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/aruvqan/32/2891_2.png) [@aruvqan](https://boards.straightdope.com/u/aruvqan)\ **Post date:** [November 5, 2021, 10:15pm UTC](https://boards.straightdope.com/t/ct-with-contrast-and-metformin/953820/9 "2021-11-05T22:15:09Z")
AFAIK unrelated, it is like a niacin body flush or IVP making me feel like I just did about 4 shots of vodka [I feel that warm down the throat and spreading out alcohol effect with whichever contrast they use for IVPs] Ever get the funky saline taste/smell from the saline push before they add contrast? Now that is wierd! ---
**Author:** ![susan](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/susan/32/17537_2.png) [@susan](https://boards.straightdope.com/u/susan)\ **Post date:** [November 5, 2021, 10:21pm UTC](https://boards.straightdope.com/t/ct-with-contrast-and-metformin/953820/10 "2021-11-05T22:21:29Z")
Amplified if you have metal dental crowns. My understanding is that the iodine causes a flush that you feel as it spreads through your body. The tech I had today narrated what I was feeling with perfect timing, which was fun (“now you feel warmth as it moves down both legs, now you have a surge of overall flush…”). ---
**Author:** ![aruvqan](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/aruvqan/32/2891_2.png) [@aruvqan](https://boards.straightdope.com/u/aruvqan)\ **Post date:** [November 5, 2021, 10:27pm UTC](https://boards.straightdope.com/t/ct-with-contrast-and-metformin/953820/11 "2021-11-05T22:27:42Z")
I actually like the iodine warmth, it is really neat. Not sure how it would be for someone like a 5 year old that doesn’t understand what is going on =( ---
**Author:** ![susan](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/susan/32/17537_2.png) [@susan](https://boards.straightdope.com/u/susan)\ **Post date:** [November 6, 2021, 1:32am UTC](https://boards.straightdope.com/t/ct-with-contrast-and-metformin/953820/12 "2021-11-06T01:32:38Z")
Some aspect of a CT has got to be a source of entertainment. ---
**Author:** ![Senegoid](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/senegoid/32/6606_2.png) [@Senegoid](https://boards.straightdope.com/u/Senegoid)\ **Post date:** [November 6, 2021, 8:23am UTC](https://boards.straightdope.com/t/ct-with-contrast-and-metformin/953820/13 "2021-11-06T08:23:27Z")
> [@aruvqan](#): > > I actually like the iodine warmth, Especially if you’re in the emergency room at 04:00 in the morning (ever notice how chilly hospitals are?) I kept asking for more! ---
**Author:** ![BigT](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/bigt/32/12044_2.png) [@BigT](https://boards.straightdope.com/u/BigT)\ **Post date:** [November 6, 2021, 8:56am UTC](https://boards.straightdope.com/t/ct-with-contrast-and-metformin/953820/14 "2021-11-06T08:56:36Z")
I started shaking uncontrollably after my contrast test on my lungs when I was having chest pains (and my heart was fine). Not even the stuff going in was enough to get me warm, but its loss was enough to make me feel colder. It’s weird how much cooler it feels than it actually was. It’s 32 degrees outside, so like probably 50 or so in here, but I’m not shaking like that. (It’s too much hassle to get the heater working when the temp is going go back up in a couple days.) ---
**Author:** ![Senegoid](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/senegoid/32/6606_2.png) [@Senegoid](https://boards.straightdope.com/u/Senegoid)\ **Post date:** [November 7, 2021, 2:04am UTC](https://boards.straightdope.com/t/ct-with-contrast-and-metformin/953820/15 "2021-11-07T02:04:44Z")
Point of information: Contrast may be used with CT scans or with MRI scans. But the chemicals they stick into you for those two cases are entirely different stuffs, AFAIK. This could become relevant if they were to ask you if you have ever had a bad reaction to contrast. When I had that CT with contrast (see two posts above) they asked me if I had ever had contrast (yes I had) and if I had ever had a bad reaction (I told them I had not). In fact, I realized later, that wasn’t quite right. I had previous contrast with a MRI and NO previous experience with contrast during a CT. So it was actually unknown if I might have a bad reaction to this. (Spoiler: Nothing bad happened.) ---
**Author:** ![susan](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/susan/32/17537_2.png) [@susan](https://boards.straightdope.com/u/susan)\ **Post date:** [November 7, 2021, 2:10am UTC](https://boards.straightdope.com/t/ct-with-contrast-and-metformin/953820/16 "2021-11-07T02:10:00Z")
I’m 35 hour out from the CT and my hand and arm are still slightly swollen. I’m wearing anti-lymphedema compression garments and doing frequent manual lymphatic drainage. ---
**Author:** ![nearwildheaven](https://avatars.discourse-cdn.com/v4/letter/n/90db22/32.png) [@nearwildheaven](https://boards.straightdope.com/u/nearwildheaven)\ **Post date:** [November 7, 2021, 2:15am UTC](https://boards.straightdope.com/t/ct-with-contrast-and-metformin/953820/17 "2021-11-07T02:15:05Z")
When I had an MRI in 2017, they injected gadolinium contrast halfway through. I had a weird sensation in my pelvis but wasn’t sure what it was. The technician did tell me that it was in my bladder, and was totally normal.