If it’s not registering the weight you have the wrong scales, or you have a cheap scale which isn’t accurate or consistent. Some cheap scales have a problem of not registering weight until it reaches a certain amount like 0,1 grams and after that they can measure every 0,01 or 0,001 grams. So they will not measure anything until the 0,1 and after that they can measure 0,11, 0,12 etc. But this is kinda problematic if you want to measure 0,040 for example. One way to get around this a little bit is by not zeroing out the scale, not pressing the -0 button, and have a container on the scale which gives a weight and then adding what you want to measure. Best thing is to buy good scales though, scales which have this problem are often not very consistent even with the above mentioned ‘fix’. I’m new to the forum so I’m not sure if it’s ok to talk dosages, since this is a very personal thing and I’m not sure if it is dependant on body weight or other personal situations. But it’s safe to say you need a scale which can measure 0,001 grams.