There are many different ways in which to use human growth hormone, I will break it down into 3 categories. These dosages I am giving are my personal opinion and are for educational purposes only, I also only recommend using pharmaceutical grade HGH as the Chinese stuff that many use is rubbish and almost always fake or underdosed and so the dosages for Chinese HGH would be a lot different than when using pharma HGH.
For anti-aging benefits you need a very low dosage of HGH, generally, people older than 50 use HGH for its anti-aging benefits. A dosage of 1 to 2 iu a day is more than enough to get significant benefits from HGH.
This is probably the most common use for HGH, the weight loss benefits related to human growth hormone use can be significant. A dosage of 2 to 4iu a day for weight loss is perfect, 2 iu is fine and will lead to significant fat loss benefits, but if you can afford it, then 4 iu would give better results.
This is where it gets expensive, HGH needs to be taken at large dosages for decent muscle building benefits, 5 to 10iu a day is what is required. 5 iu is considered low when it comes to building muscle, but it will work, if you are a serious bodybuilder and can afford it, then 10 iu is what you should be looking at.