When my hemoglobin was 25 it was so thick it kept coagulating inside the needle stopping the flow of blood. I had to use a 16 gauge needle I believe. If I try this again I’ll most likely take an aspirin before hand. Yes, it will slow down the coagulation of blood when you’re done with the procedure but I’d just hold my hand on the vein for a few minutes after pulling the needle out until it stops bleeding.
The hardest part was keeping the needle in the vein during the entire process of letting a pint of blood out. Hopefully your girl has steady hands and doesn’t mind holding the needle in place for the 5 minutes it’ll take to get the blood out.
This is how I did it. I put a 16 gauge 1 inch needle in my largest arm vein, slowly pull the plunger out of the 3cc syringe without pulling the needle out of the vein which isn’t easy at the point you have to pull the plunger fully out of the syringe. Pulling it fully out creates a vacuum that allows the blood to flow out of the barrel of the syringe. I drained the blood into a one liter protein shaker cup so I could accurately measure the amount of blood taken out. The blood will appear thick and oily which really opens your eyes to how bad it is to have high hemoglobin. That oily blood clogs the arteries. Once the one liter protein shaker cup is full of blood, pull the needle out of the vein and hold pressure on the vein for several minutes until the blow stops leaking out. I drained the blood into the shower drain with hot water running so it didn’t clog up the drain.