My NAD+ cartridge/vial isn’t filled to the top, is this normal?

YES.

Your cartridges can contain 3ml when filled to the top, but doing so makes it much more likely for the bung to come out in transit.

As a result, we sent you two cartridges with just over 1.5ml in each. We slightly over-fill each cartridge so you get every dose you need throughout the month, despite losing a few drops along the way (clearing any bubbles, discarded with the needle, human error etc).