can't answer that without knowing your tolerance to opiates and the potency of the H along with how you are going to use it.
To be safe, just use the H, small amounts until you get where you want to be.... but seriously H is such a bitch to have in your life and it's near impossible to use it just once, if you love opiates you'll more than likely use H more often as time goes on and your pharms don't work as well as they did before. Or if you prefer another opiate and run out H always seems to be around. It really is a life altering decision. Just be safe. I don't regret trying H, but trying to get it out of my life completely is HARD!
Really need more info to answer your question though, do you take benzos regularly or drink? things like that can be deadly if you don't have a tolerance and even if you do it can be risky to combine them all.