You have enough blood, DeathMetalMum, you are just good at hiding your veins by the sounds of it. Common, not at all pleasant when you are pregnant and people will want to get blood or even iv access during labour sometimes.
Being dehydrated or cold does not help.
I am very good at taking blood and would stipulate it does not so much matter who takes your blood (ie dr, nurse, midwife, phlebotomist), but how much practice they have. It is a manual skill, the more you do it, the better you get.
The needle/syringe combo avoids the vacuum from 'normal' blood taking kit which can be too strong for the walls of some people's veins and simply 'sucks' them together and nought comes out. With the syringe the blood taker has more control over how much suction they use.
I have terrible veins and on one memorable occasion had somebody dig around my feet trying to find access, so huge sympathies.
I find having my arms up to my forearms in warm water before giving blood helps as does generally being warm. I also know exactly where my best vein is and insist that it gets used. Yes, I am a bolshy moo, but I also do not like pain...
Good luck and an experienced blood taker next time
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