The one I like to take at night is Life Extension 300mcg (.3mg) 6 hour timed release (they make a bunch of different ones), which is the closest to natural melatonin release of any supplemental melatonin I've seen, although it sounds like there is massive variation between people in how much makes it to the blood from a given dose. There are a couple of ways to use melatonin and for circadian use a small non-delayed dose earlier may be better (or use both):
I have had issues waking up more frequently when taking melatonin. It sounds like while not common this side effect is not that rare either. Based on my severe sleep issues (primarly circadian) I suspect that one part of "sleep issues" for many people is actualy waking up issues and that the detailed process around waking up has a bigger influence than is currently appreciated. I suspect one reason that melatonin is helpful is that it sets the stage for a better wake up, however if something causes this wake up procedure to start after not enough sleep it can be more difficult to get back to sleep. The delayed release seems to help quite a bit to limit the chance of this happening for me, although it does still happen at times. I'm not sure if melatonin is a particularly good option for staying asleep.
Unfortunately, there aren't particulary good options. Magnesium is the easiest and as effective as anything for me but unfortunately a high enough dose to be effective will also make me tired the next day. However, if your diet is low on magnesium then just increasing that some might help or possibly you won't have the issue with tiredness the next day. baclofen helps me but has issues and I certainly would not recommend it for your case.
A short (few minutes) nap mid day helps the circadian rhythm but longer naps can make it harder to stay asleep at night. If you nap for longer periods, multiple times, or later in the day that is the first thing I would suggest changing. I'm not sure what length causes more trouble but I think getting to sleep but staying asleep as briefly as you easily can is the ideal (though if you will naturally wake up after a bit longer that might be better than an alarm).
I also noticed covid made my already bad sleep worse when I had it (most likely covid, not confirmed by test; cold or flu usually give me better sleep for a day or two). However, I didn't notice any lasting issues (I still have severe sleep issues but it was just that first week of covid that they seemed to be different from usual). I wonder if it could be just your memory of how you sleep that changed after you noticed it due to the disruption. As long as you can easily get back to sleep and aren't staying awake for long it should not cause trouble and is not uncommon. If you feel rested there is nothing to fix while worrying about it or trying to change it could case worse trouble.
These are my thoughts anyway, hopefully something in there is helpful :).
https://circadiansleepdisorders.org/treatments.php#melatonin
I have had issues waking up more frequently when taking melatonin. It sounds like while not common this side effect is not that rare either. Based on my severe sleep issues (primarly circadian) I suspect that one part of "sleep issues" for many people is actualy waking up issues and that the detailed process around waking up has a bigger influence than is currently appreciated. I suspect one reason that melatonin is helpful is that it sets the stage for a better wake up, however if something causes this wake up procedure to start after not enough sleep it can be more difficult to get back to sleep. The delayed release seems to help quite a bit to limit the chance of this happening for me, although it does still happen at times. I'm not sure if melatonin is a particularly good option for staying asleep.
Unfortunately, there aren't particulary good options. Magnesium is the easiest and as effective as anything for me but unfortunately a high enough dose to be effective will also make me tired the next day. However, if your diet is low on magnesium then just increasing that some might help or possibly you won't have the issue with tiredness the next day. baclofen helps me but has issues and I certainly would not recommend it for your case.
A short (few minutes) nap mid day helps the circadian rhythm but longer naps can make it harder to stay asleep at night. If you nap for longer periods, multiple times, or later in the day that is the first thing I would suggest changing. I'm not sure what length causes more trouble but I think getting to sleep but staying asleep as briefly as you easily can is the ideal (though if you will naturally wake up after a bit longer that might be better than an alarm).
I also noticed covid made my already bad sleep worse when I had it (most likely covid, not confirmed by test; cold or flu usually give me better sleep for a day or two). However, I didn't notice any lasting issues (I still have severe sleep issues but it was just that first week of covid that they seemed to be different from usual). I wonder if it could be just your memory of how you sleep that changed after you noticed it due to the disruption. As long as you can easily get back to sleep and aren't staying awake for long it should not cause trouble and is not uncommon. If you feel rested there is nothing to fix while worrying about it or trying to change it could case worse trouble.
These are my thoughts anyway, hopefully something in there is helpful :).