It's safe for adults at least 21 years of age to get lip injections. The best age to get lip injections depends on your personal goals and desires. For some people, getting lip injections earlier in life is a way to achieve a fuller, more defined lip shape. But for others, waiting until they're in their 40s or later is a better option. Lip volume and definition naturally decrease with age. Getting lip injections can help restore volume and definition, creating a more youthful look.