ATB funnily enough I had the same problem last time with my blood test after never having an issue before (though it doesn't sound nearly as bad as your experience). Just in case it's helpful: it was first thing in the morning and I realised that I hadn't had anything to drink except a coffee and a few sips of water and the nurse said it really makes a difference how much water you've drunk, particularly in the morning (she explained the science as to why but I forgot!). So I'll be drinking plenty of water in advance next time!
Might have been just not a great nurse for you, but thought I'd mention it in case it's helpful!
Also - I didn't realise you couldn't get a Testosterone prescription on the NHS, that's bad!!