Never went past 2.5 because of how it affected me, I'd genuinely struggle to reach 800 calories some days. Just focus on getting protein in before anything else. Being vegetarian made that even tougher for me. Snacking on nuts, Greek yogurt, and strawberries throughout the day helped a lot. Smaller, more frequent meals beat three big ones for me. If you own a blender, a morning smoothie is an easy win, Greek yogurt, protein powder, berries, and a greens powder actually pack in a surprising amount, and drinking something is always easier to force down than eating when you're not hungry. Dropped 24lbs in the first 24 days, then it slowed considerably. Stayed on it five months total, lost 3.5 stone overall, then got pregnant after six years of trying. Didn't lose any hair, though I had a whole regimen of supplements going at the time.
Edit to add, my prescription is still written for the 5mg pen, and I just count clicks to pull out 2.5, easy enough and it cuts the cost dramatically!