What type of anticoagulant can we use for our blood vial jewelery?

My boyfriend and I have decided that we want to do blood vial jewelery. He'll wear a vial of my blood around his neck, and I'll do impossible to tell apart. We have the 'fill your own jewelery', and sterile needles and syringes to do this. But if we don't use some sort of anticoagulant won't the blood dry up in the vial and get adjectives icky looking. We want it to stay fresh and red. What could we use to achieve this? It has to be something we can order online or buy over the counter. Thanks.

Also, please don't answer if you're going to be rude or criticize us for our choices.
Answers:
Heparin, citrate, or EDTA (ethylene-diamine-tetraacetic acid) are used in blood testing to keep blood from clotting while contained by the test tube. However, I don't know a good way to take a hold of any of them. I would do an online search for them.


By the way, I know you said not to reply if you're going to criticize, but I can't help it... That is completely disgusting and don't know why you would want to do it. I hope neither of you own any bloodborne diseases. Also, taking someone's blood is very dangerous if you're not trained in phlebotomy.
What's wrong with exchanging locks of each others hair? Is this because Billy Bob and Angelina did it? They both own mental problems.
The blood, regardless of how you anticoagulate it, will achieve old and discolored, probably hemolyzed with time. You might want to consider some sort of container that you can change the blood out when needed.

A little unsanitary, but afterwards again, I assume you are swapping bodily fluids already.

If you want an alternative, think about braiding a thin lock of respectively other's hair, making a loop of it and putting it through some random piercing (nose, eyebrow, naval, or other). More original than the blood entry.

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