CGM/ Dexcom users can experience the exact effects of Nyquil without using acetaminophen.
It is @Irish’s thread on the subject that awakened a home pressure-point for me: my wife uses Nyquil like Irish, and we have that long-standing discussion: the interesting thing about Nyquil is that you do NOT need acetaminophen if you want the drowsy effect of Nyquil.
Nyquil’s ingredients are:
- acetaminophen (pain reliever/ fever reducer)
- dextromethorphan (supposedly a cough suppressant but the AMA says not…)
- doxylamine succinate (anti-histamine)
The feeling of sleepiness most (but not all) people get from Nyquil is primarily from the doxylamine succinate, a standard side-effect of many anti-histamines. There may also be a weaker but similar effect from the dextromethorphan (which, btw, is quite ineffective as a cough suppressant…).
But the acetaminophen has no sleeping effect at all. It just makes you feel better by lowering fever (not always a good thing for sickness) and relieving pain. Ibuprofen does that too.
You can get exactly the same effect as regular Nyquil by buying any drug that has doxylamine succinate and dextromethorphan, and adding some ibuprofen. For instance, Nyquil Cough has just dextromethorphan and doxylamine succinate.
So, if you have a Dexcom and want to use Nyquil, you could simply buy some Nyquil Cough and combine it with Ibuprofen 
.
How I found out: my T1D son, when he was younger, had asthma, and would cough for a week non-stop, every 4 seconds, every time he got a respiratory bug. It was a horrible thing for a parent to hear. So I boned up very heavily on everything I could do to help him through the night with the awful cough he had. I did eventually figure out a solution btw, although his doctor was not totally a fan of it.
You can verify most of my assertions above on this post from the Consumerist, btw.