Yes blood work very necessary to know where you are at accurately, but let me tell you if you are shooting already you can feel the need of it. For example me what tells me is to feel my skin thick after a meal, personally am a very, very discipline with my food so when i feel the back of my neck is getting thick or my lower back area…i know what it is…estrogen levels getting higher and lately i know exactly where it comes from: I have increased the work outs , am training 4 days and rest the 5th and start again and i have been taking a 50 mg TNE shot before every work out; i just went up to 0.5 mg/day and i started about 2 weeks ago with 0.25 EOD