If you draw up some blood in the syringe, there is no need to pull the needle all the way back out and waste the sharpness to reinject. Veins and blood vessels are thin and small. If you aspirate and some blood draws into the syringe, just pull the needle out a little, (not the whole way), and re-angle it, push back in the rest of the way, aspirate again and your good to go. If you would happen to inject into a vein, especially with an oil based substance, you put yourself at risk for a stroke or even worse. Oil seperates with blood, just like it does water, so you could be in some trouble if you don't aspirate. Hope this helps
Be Safe
