Re: blood testing
Depends on the model, but the one I had was about the size of a mobile phone, maybe a bit squarer. Can feel a bit odd, but I think working would be ok. Have a think whereabouts (side, front or back) the monitor is least likely to get knocked when you're working and clip it to your belt there. I found it best clipped to my waistband but with the monitor box inside my trouser waistband and held against me by the waistband, rather than on the outside like you would with a phone. That way it jiggled about less when I walked so I was less aware of it. There's a long lead between the sensor and the monitor, so you can reposition it easily. They usually supply a plastic bag that hangs round your neck so you can shower - you could always use one of those under your overalls at work if not practical on your waist.
Most monitors last for 72 hours so you'd need to take 3 days off if that's what you decide. But I think better to work if you can, so you're in your normal routine. Otherwise the readings may not show your usual pattern and the results would be less useful.