NAD+ injection is terrific. NAD+ was the biggest improvement, for me anyway, of everything I've tried. I'm 60, have Hashimoto's, and survived septic shock. I was on lots of meds, which led to inflammation, weight gain, fatigue, and brain fog. My NAD levels were probably bottoming out.
I started low at 25mg. I noticed effects within 45 minutes. I felt a tingling in my legs (which felt great) and my brain felt scrubbed with menthol. My energy skyrocketed (but not jittery), and I felt alive again. I got off my prescriptions within weeks.
Weirdest part of my NAD+ journey: it improved my eyesight. I thought, 'no way'...but my glasses didn't work for driving. I found studies on pubmed and nih about NAD+ and age-related vision loss. So, NAD+ will always be in my toolkit.
I take 50mg every other day. Precursor supplements take more time to build up.