I have a small mouth and thin lips. What are my options to make my mouth bigger and fuller lips?

Dermal fillers, such as Juvederm and Restylane, work very well in the lips and can be used to provide both volume and definition.  Both of these products are made from hyaluronic acid, a gel-like material that naturally occurs in the human body.  I would recommend that you seek out a consultation with a cosmetic practice with extensive experience in the use of dermal fillers.  

Thank you for your question. In my office I like to use dermal fillers
such as Juvederm and Restylane Silk for lip augmentation. These are hyaluronic
acid fillers that can easily be dissolved with an enzyme known as hyaluronidase
if you are unhappy with the results. I recommend having a consultation with an
experienced and talented injector to determine the best treatment plan for you.
Best of Luck! 

You can increase the size of your lips with dermal fillers like Restylane, JuveDerm and Belotero. They all will increase the appearance of your lips. Only use skilled injectors who know what they are doing. You cannot make your mouth bigger in a non-invasive manner. 

Practically you have two choices. 1) You can do a filler which is easy and will last perhaps up to 9 months in some patients (juvederm is my filler choice for lips)                                                       2) You can do a Dermal-Fat lip graft procedure and get a permanent enhancement of your lips from your own tissue. This is a procedure I invented 25 years ago to get a more permanent result without using artificial materials. The drawback for young patients on this procedure in the 2 inch supra-pubic scar from the donor sight. I only do this in younger women if they already have a C-section scar                                                       3) ABSOLUTELY do not put anything artificial in your lips as an implant, they ALWAYS extrude and need to be removed