Yep. That's the thing... you don't know. In fact, you could get one batch that works great and the next batch, from the same company, might not be as pure. That said, some people don't experience hunger on MK and some don't have any negative side effects from Melanotan. If you hit the tanning spa twice a week with Melanotan, you'll know in a couple of weeks. Here's how I dosed Melanotan for my research: https://livelikeaviking.com/topic/reconstitute-melanotan-2/. I haven't been out in the sun for over a month and I still look very tan.