Will half a syringe of Juvederm be enough for my already full lips? (Photo)

Thank you for sharing your question and photographs. Unfortunately without knowing what your goal results are it is difficult to offer definite advice but half of a syringe of Ultra will offer a subtle appearance change to your lips and if you are splitting it between your upper and lower even more so.  Have representative goal photographs in mind when you go to your appointment so that your injector has a better visual idea of what you want to achieve.  Hope this helps.

Most advanced injectors have moved beyond using Juvederm and are incorporating the Vycross products such as Volbella and Vollure for their lip injections.  In your case, you already have a good amount of volume and so I would strongly recommend using Volbella which actually does come in a 0.55cc syringe so that you wouldn't get excessive volume.Make sure that you ask about the experience and expertise of your injector.  The person behind the syringe makes all the difference between a good result and a not so good result!  I hope that helps!Warmest regards,Gregory A Buford MD FACSBoard Certified Plastic Surgeon and Author

You would get a nice result with half a syringe. I prefer to use a micro cannula to inject the lips to prevent bruising. Look for a cosmetic dermatologist or plastic surgeon who is an expert in fillers. 
I hope this helps.