Post-COVID shot carb ratios

Hey there,

Has anyone had their second dose of COVID-19 vaccine and seen a change in their carb ratio and/or basal rate needs? I had my second shot of Moderna last Tues, so I’m one week out until estimated immunity really kicks in. In the meantime, my longtime carb ratio and basal rates have become completely inadequate and I’m contending with soaring blood glucose levels and ketones as I fiddle with increases. Any sharing of experience is much appreciated! (I use a Dexcom G6 and an Omnipod pump)



I get my second dose (Pfizer) next week so am really looking forward to some guidance!


After my first shot, arm was sore and I felt unwell the next day. Administering nurse for shot two said a lot of people were having stronger reactions to the second shot, which I had also heard from others who’d already had it. I was fine the afternoon of the shot but woke up the next day with a fever of 100.1, aching joints, and fatigue. Generally felt like a bad bout of flu, and shot site was pretty painful. Followed my regular sick day protocol and luckily had been able to clear my calendar in anticipation of reaction, because I was in bed all day. Sick feelings abated the next day, but insulin issues remained.

Good luck, CatLady! And sign up for V-Check


Hi Leah.
I didn’t get the vaccine yet. But when I had Covid my insulin requirements went way up during that time. Don’t know if what you are seeing is a similar cause, but since the vaccine kind of “tricks” the body into believing it’s infected, seems like that might make sense.


After my first Moderna my arm was sore and my insulin requirements went up about 50% just like it would if I was sick with a cold. After about 48hrs it was back to normal. I was encouraged that my insulin requirements went up. It told me my immune system was reacting and learning to recognize covid.


I received my first Covid shot last week (Moderna). My arm ached if moved it just right/wrong and if I pressed on the injection site, but other than that no real reaction. I tend to “wander upwards” out of target range in the afternoon or evening if I’m sitting watching TV or otherwise inactive, unless I’m asleep and then tend to “wander downwards” but not low. The first few days after the shot, the upwards trend was more pronounced with one very quick increase from 120 to over 210 (that’s high for me). It seems to have settled back down to normal “ranginess.” I’m hoping the second shot will have similar “minor” reactions.


I just had an endo appt. and asked my endo what she is hearing about this from her patients. She (as expected) said that both vaccines are affecting individuals differently but the second shot of both has generated the most calls to her about spiking BG among other more well publicized side affects. She volunteered that the majority of her diabetic patients who were vaccinated (mostly over age 65) have had higher than normal insulin requirements for less than a week after the second shot.


Thanks for the caution and info. I’m 66 and headed back for my second Moderna shot in a week. The first one gave me a somewhat achy arm, but nothing significant. Have heard from several people I know and the news that the second shot had stronger impacts and wondered what additional “fun” I could expect from T1D!


Already posted this in anohter thread. Had the opposite reaction to my second Pfizer shot:

I had nothing after my first Pfizer shot on Feb 3. But got my second Pfizer shot on the 24th and did experience lows after. Also found that my Dexcom G6 plummeted and stayed there even though I ate many doughnuts and my blood sugar rose back to normal–Dexcom showing 45 and finger stick showing about a hundred points higher. Calibrated, calibrated again. Changed sensor, same result. Changed transmitter (but with same second sensor) same result. Sensor blanked out, but before I got around to changing it the number came back and now it is ok. After a couple of days everything seems normal again, both my sugars and the Dexcom response. Wish I had documented the sequence to report to CDC and Dexcom. I can’t really untangle it now. Only other symptom both times was a very sore arm, reminding me of the plague shots I got in the 1960’s.

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Wow, what an ordeal! Clarity will have a record of most of your experience, e.g., showing gaps when you started a new sensor. I bet there is a way to get the info to CDC through your doctor or on their website.

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Actually, they have an app you load on your phone and report your experience, but I have not tried it yet.

And the Dexcom did another bottom-out about an hour ago. I will call them tomorrow.


V-check , the CDC app, is easy to use and pretty useful - they send reminders to fill out quick daily or weekly follow-up surveys. Each one had a comment area so you can specify D issues. https://vsafe.cdc.gov


Thought I’d post a follow-up on my reaction to the second shot (Moderna). It took about 10 days for my insulin needs to go back to normal. I used temp basal rates rather than set a new basal program on my pump, because I wasn’t sure how long it would be. For me, it roughly tracked with the time my body was building the immune response after the second dose.


2 posts were split to a new topic: New T1D, Wondering what your Sick Day Protocol looks like?