I take magnesium bisglycinate for sleep and have no issues getting up to exercise in the morning. I’m not sure what the logic would be for making you tired the next day? You may just not be getting enough sleep?

I'd also try a week or 2 without it, OP. And if you feel better experiment with the form or time of doseage, maybe even a magnesium oil or Epsom salt baths.

The grogginess sounds miserable, I don't think it is just age. Do you possibly have apnea? That could cause grogginess. I believe there are at home sleep tests now.

As a data point of one, I also take that same dose at night to help with my sleep cycle. No idea if it’s actually doing anything. Not in perimenopause (40s M). I haven’t noticed any issues like you describe in the morning. To include getting up super early to get in long workouts of 3-5 hours and also when racing.

Maybe just try dropping it for a week and see how you feel. I don’t think it’s like a drug that requires a steady state. I think it’s either absorbed or not. So dropping it for a week or even a day might eliminate any impact it’s having on you.

When I was trying magnesium supplements, I noticed a big difference between the different compounds - citrate, oxide, glycinate, etc. Maybe you could try seeing if a different form doesn't still drag you down in the morning?

I take 400mg Mag Glycinate around 10pm at night to help manage perimenopause sleep issues. I’m also on an estrogen patch - I’ve been taking both for over 6 months and my sleep issues/night sweats are much improved.

But I’m a morning runner and boy I’ve been struggling with lack of energy and just moving slow. It’s harder to get out the door, start running and such an effort to push my pace.

I go ~3 miles and try to run 5 days/week - I do stretching and strength training. I eat a little food and caffeine first thing. I used to run 25 miles/week but that seems like a stretch now. I’ve been a lifelong runner but now 3 miles feels hard to complete.

I know Mag Glycinate is supposed to have a relaxing effect. Could it be impacting my morning energy?
Maybe I’m just a lady in mid-fifties whose slowing down sigh.