I just did a bit of reading about sythroid, which I hope you have also done… right?
So it looks like the suggestion is to wait 1-2 hours after the sythroid for it to get far ahead of your food so it can be absorbed in intestines. Regular breakfast then spends some time in the stomach before it moves into the intestines and hopefully the sythroid would be mostly absorbed by then.
I also read that synthroid would rather attach itself to minerals like iron than to be absorbed, which would make it much harder for the body to use it (or even impossible)
Now I wonder if the 4 hour time recommendation between synthroid and iron supplements is due to how available the iron supplement would be (considering that it would be a huge amount in either pill or liquid forms) compared to the availability of iron in Huel. Huel has extra iron because they compensate for phytic acid from oats that might otherwise combine with iron (it turns out a lot of things like to grab onto iron, locking it up in molecular bonds)
So, I don’t know if you can go 4 hours from wakeup+meds to wait for breakfast or if you can do only 2 hours, counting on Huel as more like food than an iron supplement - but you probably know how you feel with and without the full and proper effects of the synthroid… are you noticing that you might be adversely affecting absorption?
You will definitely want to discuss your numbers with your doctor if you are getting better nutrition than you used to get. A metabolic panel might show a very different picture after 2 months using Huel to get nutrition you might not have been getting from your diet last time you saw the doctor.
I hope this helped. I’m not a doctor and I can’t really give any sort of official doctor-y opinion. I am curious though what your doctor says, so please do post an update then.