Not an expert in drugs, but that's why you never dose it in its pure form, it's just impossible. 2mg and you're dead.
So you weight 1 gram and mix it with let's say 1000g of another inert substance to make its concentration manageable.
Now, 1mg dose is 1g of product, a slightly overdose of 1.2g won't kill you.
The problem now is in the mixing homogeneity, must be absolutely perfect, or you'll risk taking the "spicy" salt pinch.
Not the scale problem, but the procedure.
Anyways, that's why you don't mess with fetanyl. It's like playing with a 100KV pole and a copper rod, "how close can I get?" LOL.
I got it administered several times during my long stance in the hospital few years back. I must say it's a hell of a drug.
Makes you feel in heaven, forget all problems, like when you were a child and it was the last school day before summer holydays.
Thankfully all I need to keep my mood is some ocassional nachos & bacon!