Ideally, keep it away from light, sealed tight blocking out air, and in a fridge if it’s mixed, or in a freezer if it’s still in raw powder form.
I personally put my RU mixed solutions in the fridge in 50ml bottles, and my RU raw powder in a Ziploc bag sealed tight and then I put that in a little container and leave it in my freezer.
while preventing hair loss just as effectively, if not more so.
The user feedback and academic resources on RU suggests that RU is the MOST PROMISING SOLUTION to male pattern baldness (and other DHT-related conditions) that exists today.
DHT (a necessary and otherwise useful hormone) attaches to and shrinks hair follicles in those prone to MPB (male pattern baldness).