Hi I am a licensed tattooist with my own studio, I should think that post op, once everything has settled down you would be fine, I tend to tell people to have a sugary drink and some food before a tattoo, but in fear of dumping I would say plenty of water and some food. Make sure you have finished your blood thinning meds before hand! Just tell your tattooist that you are post op and if you start to feel weird then any good tattooist will stop and recommend that you come back for a 2nd sitting when your ready.
Hope this helps
Steve