An in-the-flesh examination of the lips is absolutely essential for determining not only which lips require treatment, but what injectable material(s) would be best and precisely how much will be required to create natural-looking lips that have appropriate symmetry and balance.
Unfortunately, all too many inexperienced injectors have created lips that in side view look
"duck like" or what has been called the "trout pout" and in front view appear like "sausage" lips. This comes from a lack of awareness of the appropriate and natural proportions of the lips in relation to each other and to the surrounding skin and that any exaggeration of these proportions can give rise to the undesirable results just described. The intent of treatment is not to have a person's lips enter the room before she does.
For lips to look natural, the upper lip, in side view, should project slightly more than the lower lip, in a ratio of approximately 1.5X more than the outward projection of the lower lip. In front view, the ratio is reversed. In vertical height, the ideal lower lip should be approximately 1.5X that of the upper lip. For the body of the lips, I generally prefer Juvederm UltraPlus XC.
Besides keeping these proportions in mind, treatment with fillers and/or volumizing injectables, must also be directed, when appropriate, to other detractors of the lips. These include, if also present, absence or flattening of the philtrum and Cupid's bow and loss of border definition, "lipstick bleeding" lines (aka "smoker's lines), diminution of the so-called "white roll' that defines the separation between the red lips and the skin above and below the lips. For the philtrum and Cupid's Bow, I have found Restylane L helpful; for smoker's lines, Belotero Balance; and for the vermilion border, Juvederm Ultra XC.
From the above, it should go without saying that consultation and treatment by a board certified aesthetic physician with extensive experience in treating the lips is crucial for a gratifying outcome.