Published 31 October 2026 · Reviewed by Dr Sin Yong
A lip flip is a small dose of botulinum toxin placed into the orbicularis oris, the ring of muscle around the mouth, so that the upper lip rolls outward slightly, most visibly when smiling. It adds no volume and is shorter-lived than lip filler. In Singapore botulinum toxin is a prescription medicine given by a doctor, after the lips are assessed at rest and in movement.
Short answerA lip flip changes how much of the upper lip shows; lip filler changes how much lip there is. Which one fits is decided by looking at the lips at rest and on smiling.
A lip flip is an injection of botulinum toxin into the orbicularis oris, the circular muscle that purses and closes the lips, placed just inside the upper lip border. When the outer fibres of that muscle relax, they curl the lip inward less, so a little more of the pink part of the upper lip (the vermilion) rolls outward and shows, especially on smiling.
Illustrative image — not a patient.
The change is in position, not in quantity. A 2026 prospective study of 17 women measured the upper lip with 3D imaging before and after treatment and found a modest but significant increase in upper lip height with no change in lip volume, which the authors described as projection through muscle relaxation rather than augmentation. A 2025 systematic review of seven studies reached the same picture: consistent upper lip eversion and improved contour, with mild, transient side effects such as difficulty whistling or drinking through a straw. An earlier 2021 case series of three patients, also measured with 3D imaging, found a larger upper vermilion height after treatment, alongside slight, temporary weakness of the muscles around the mouth.
Botulinum toxin is a prescription-only medicine in Singapore and is injected by a doctor. Several formulations are registered, each measured in its own units, and BTX is the site's shorthand for the class rather than any brand. The botulinum toxin glossary entry explains how it works.
Lip flip vs lip filler: which problem each solves
A lip flip and lip filler answer different questions: filler adds material to a lip that is thin or has lost its border, while a lip flip changes how much of an adequately sized upper lip shows when the muscle pulls it in. Choosing between them starts with watching the lips move.
Option
What it does
What it cannot do
Tends to suit
Page
Lip flip
Relaxes part of the orbicularis oris so the upper lip rolls outward slightly
Add volume, define the border or change the lower lip
An upper lip that thins or disappears on smiling
This page
Hyaluronic acid lip filler
Adds volume and defines the border and Cupid's bow; dissolvable with hyaluronidase
Shorten a long upper lip or stop it rolling in on smiling
Surgical lip lift, referred to a plastic surgery specialist
Removes a strip of skin under the nose to shorten the upper lip
Add volume; it leaves a scar under the nose
A long upper lip that covers the teeth at rest
Referral
Some plans use both, in sequence: a lip flip for a lip that rolls in on smiling, and a small amount of filler for a border that has flattened. They are planned after the whole lower face has been assessed, because a recessed chin or a deep smile line changes how the lips read.
“If your lip looks fine in a relaxed photo and disappears only when you smile, more filler is not the answer. The muscle is.”
Dr Sin YongOn choosing between a lip flip and filler
Who a lip flip suits, and who it does not
A lip flip suits an upper lip of reasonable volume that seems to vanish when you smile; it does not suit a lip that is thin at rest. The test is simple: if the lip looks adequate in a relaxed photograph and thin only in a smiling one, the muscle is part of the story.
Usually suitable
An upper lip that tucks in and thins on smiling.
Someone who wants a small change in how the upper lip shows, without added volume.
A gummy smile where the lip elevators also overact, assessed as part of the same plan.
Usually not suitable, or a different plan
A lip that is genuinely thin at rest, or has lost its border with age: that is a volume and structure question.
A markedly long upper lip that covers the teeth at rest: the lip flip does not remove skin, and a surgical opinion may be the honest answer.
People who rely on precise lip control, such as wind-instrument players, singers or those whose work depends on clear speech, because a temporary change in lip function matters more to them.
Who should wait
Pregnancy and breastfeeding, neuromuscular disorders such as myasthenia gravis, infection or a cold sore at the injection site, and a previous reaction to any botulinum toxin product are reasons to defer or avoid treatment. The botulinum toxin suitability page lists what is checked.
How a lip flip is approached at the clinic
The decision comes from watching the lips at rest, in speech and on a full smile, because the lip flip only makes sense when movement, not volume, is what thins the lip. At the clinic on Orchard Road, Dr Sin Yong assesses the lip as part of the lower face: upper lip length, how much tooth and gum show, the chin and the smile lines.
Assessment. Photographs at rest and smiling; lip length, symmetry and gum show are noted; previous filler or toxin in the area is recorded.
Decision. Lip flip, lip filler, both in sequence, a gummy smile plan, or no treatment. Doing less than was asked for is an acceptable outcome of this conversation.
Treatment. The skin is cleaned, and a small dose is placed with a fine needle at a few points along the upper lip. Because the same muscle is used to speak, eat and drink, the dose is kept conservative.
Review. The result is reviewed once the toxin has taken effect, and any asymmetry is assessed in movement.
After a lip flip most people see pinpoint marks and sometimes a small bruise, and then notice the lip feels slightly different in use. The lip area is mobile and sensitive, so mild changes in function are an expected part of the treatment rather than a complication.
What is normal
Tiny injection marks and, occasionally, a small bruise.
Drinking through a straw, whistling, blowing or sipping from a cup can feel different while the toxin is active.
Some people notice it slightly when pronouncing sounds such as "p" and "b".
When to call the clinic
Liquid escaping from the mouth when drinking, or difficulty closing the lips.
A noticeably uneven smile.
Swelling, redness or pain that increases rather than settles, or any difficulty swallowing or breathing, which needs urgent medical attention.
Is a lip flip safe?
In published studies the side effects of a lip flip have been mild and temporary, and they follow from what the treatment does: a muscle that purses the lips is deliberately weakened a little. The real risks come from dose and placement. Too much, or toxin placed too deep or too wide, can weaken lip closure or spread to neighbouring muscles and make the smile uneven until it wears off. That is why the dose is conservative, why the injector should know the perioral anatomy, and why the product should be one registered for use in Singapore and handled by a doctor. Botulinum toxin bought online, or offered outside a medical clinic, carries risks that no aftercare can undo.
Common aftercare advice is to avoid pressing or massaging the area and to skip strenuous exercise and heat for the rest of the day. The downtime guide for wrinkle injections explains what marks and bruises look like.
Lip flip Singapore: how long it lasts and what decides the plan
A lip flip is shorter-lived than lip filler, because the dose is small and the muscle around the mouth is in constant use. How long it lasts varies between individuals and is reviewed rather than fixed to a calendar; filler lasts longer because the gel itself provides the shape.
What decides the plan is the muscle's strength, how much the lip rolls in, whether a gummy smile or lip lines are part of the picture, and whether filler is planned alongside. The fee follows the same logic: the dose for the zone, whether more than one area is treated, and review. The botulinum toxin cost factors guide explains each factor, and no figure is quoted before an assessment.
Questions to ask before a lip flip
Is my lip thin at rest, or only when I smile?
Would filler, a lip flip or both suit me better, and in what order?
Which product is being used, and is it registered for use in Singapore?
Who performs the injection, and who reviews it?
Your next step
1. MessageWhatsApp +65 8023 7170 with what is bothering you. A reply comes from the clinic, not a bot.
2. AssessmentDr Sin Yong examines you himself on Orchard Road, with ultrasound where earlier filler is involved.
3. A plan in writingWhat he would do, what he would not, the fee factors, and the option of no treatment.
Every treatment is performed by Dr Sin Yong personally. Singapore Medical Council registered · invited to share his clinical expertise internationally for CLASSYS, DEKA, Fotona, Hironic and Ilooda.
Bring photographs of your smile if the lip change is most noticeable in them. How consultations work.
A lip flip does not make lips bigger in volume. It relaxes the edge of the muscle around the mouth so that a little more of the existing upper lip rolls outward and shows, mainly on smiling. A 2026 study using 3D imaging found a modest increase in upper lip height with no change in lip volume. Adding volume is the job of lip filler.
Neither is better in general; they solve different problems. A lip flip suits an upper lip of reasonable size that disappears on smiling, while lip filler suits a lip that is thin at rest or has lost its border. Some people need both, in sequence. Watching the lips at rest and on a full smile at assessment decides which fits.
A lip flip is shorter-lived than lip filler because the dose of botulinum toxin is small and the muscle around the mouth works constantly through speech, eating and drinking. How long it lasts varies between individuals, so plans are reviewed rather than fixed to a calendar. If the effect suits you, a repeat is discussed at review rather than booked in advance.
A lip flip involves a few small injections along the upper lip with a fine needle. Most people describe a brief sting at each point; the lip is a sensitive area, so a cool pack or topical anaesthetic can be used. Tiny marks and occasionally a small bruise follow, and these usually settle quickly. Any increasing pain or swelling afterwards is a reason to call.
Drinking through a straw is often the first thing that feels different after a lip flip, because the treated muscle is the one that purses the lips. A 2025 systematic review listed difficulty with straws and whistling among the usual mild, transient effects. If liquid escapes from the mouth or the lips will not close properly, contact the clinic for review.
A lip flip and gummy smile treatment target different muscles. A gummy smile usually comes from the muscles that lift the upper lip pulling too far, and those elevators are treated directly. A lip flip relaxes the muscle that rolls the lip inward. Where both patterns are present they can be planned together, after an assessment of how much gum shows and why.
Yes, a lip flip and lip filler can be combined when the lip both rolls in on smiling and lacks border definition or volume. They are planned in sequence after the whole lower face has been assessed, so that each change can be judged on its own. Doing both is not automatic; for many lips one of the two is enough.
A lip flip is not suitable during pregnancy or breastfeeding, with neuromuscular disorders such as myasthenia gravis, with infection or a cold sore at the site, or after a previous reaction to botulinum toxin. It is also a poor fit for a lip that is thin at rest, and people who rely on precise lip control, such as wind-instrument players, should weigh the temporary change in function.
References
The lip flip: a systematic review of botulinum toxin lip augmentation. Archives of Dermatological Research, 2025. source
Lip Flip Revisited: Clinical Outcomes and Neuromodulatory Basis of Upper Lip Eversion. Aesthetic Plastic Surgery, 2026. source
The use of botulinum toxin A in upper lip augmentation. Journal of Cosmetic Dermatology, 2021. source
About this page: written and medically reviewed by Dr Sin Yong, MBBS (NUS), MRCS (Edinburgh) · Last reviewed 31 October 2026 · Illustrative images only, not patients · Editorial policy
