Botox vs. Letybo Units: Are the Units the Same? How Dosing Really Works

Botox vs. Letybo Units: Are the Units the Same?

No. Letybo units and Botox units are not interchangeable and should not be converted using a simple 1:1 ratio. The FDA prescribing information for both products specifically states that each product’s potency units are based on its own preparation and assay method. Therefore, a specific number of Letybo units cannot simply be translated into the same number of Botox units. Dosing should instead follow the product-specific prescribing information and the patient’s treatment needs.

If you’re looking at the broader differences between these two wrinkle relaxers, our complete Botox vs. Letybo comparison covers their approved indications, treatment areas, onset, duration, safety, and other key considerations.

At a Glance

The FDA explicitly warns against comparing or converting the potency units of these products because the units are specific to the individual preparation and assay method.

What Is a “Unit” of Botox or Letybo?

A unit is a measurement of biological activity used to describe the potency of a botulinum toxin preparation.

It is not simply a measurement of:

• Weight
• Volume
• Amount of protein
• Number of molecules
• Physical size of the injection

Most importantly, a “unit” does not represent a universal measurement that is identical across all botulinum toxin products.

Each manufacturer’s potency assay establishes the biological activity of its particular product.

This is why the FDA labeling for both Botox Cosmetic and Letybo specifically states that their potency units are product-specific.

Are Letybo Units the Same as Botox Units?

No. This is the most important answer in this article.

One Letybo unit should not be assumed to equal one Botox unit.

Likewise, a provider should not simply take a Botox dose and mathematically convert it into an equivalent number of Letybo units.

The Letybo prescribing information states:

“The potency units of LETYBO are specific to the preparation and assay method utilized.”

The Botox Cosmetic prescribing information contains essentially the same fundamental warning regarding its own potency units.

Is 1 Unit of Letybo Equal to 1 Unit of Botox?

No. A 1:1 conversion is not supported by FDA labeling.

This is an important distinction because consumers frequently see statements online such as:

“50 units of Letybo equals 50 units of Botox.”

That is not an appropriate way to compare the products.

The numerical values may look identical, but the unit systems are product-specific.

Can You Convert Botox Units to Letybo Units?

Not using a scientifically established universal conversion formula.

There is no FDA-recognized universal formula that says:

X Botox units = Y Letybo units.

The FDA specifically states that the potency units of Letybo cannot be compared to or converted into units of other botulinum toxin products measured using different assay methods.

The same principle applies in the opposite direction to Botox.

Why Can’t the Units Simply Be Converted?

The reason is more complicated than simply saying that the products are “different.”

Botulinum toxin products differ in:

• Manufacturing processes
• Formulation
• Potency assays
• Reference standards
• Biological characteristics
• Clinical dosing paradigms
• Studied indications

A 2024 review in Toxins emphasizes that botulinum neurotoxin products have product-specific manufacturing and potency characteristics and that their units are not interchangeable or convertible using simple dose ratios.

This is why the number printed on the vial should not be interpreted as though it were a universal currency shared by every botulinum toxin.

Does That Mean Botox Is Stronger Than Letybo?

No. The number of units does not allow you to declare one product “stronger” simply by comparing the numerical dose.

For example:

20 units of Product A and 20 units of Product B do not necessarily represent equivalent biological activity.

The unit number is meaningful within the specific product’s dosing system.

It should not be treated as a universal measure of toxin strength.

Does Letybo Require More Units Than Botox?

You cannot answer this simply by comparing the numbers. A provider may use different numerical doses of different botulinum toxin products. That does not mean the product requiring a larger numerical number is weaker.

The correct question is not: “Which product requires fewer units?”

The more clinically meaningful questions are:

• What product is being used?
• For what indication?
• What dose has been studied?
• What does the product’s prescribing information recommend?
• What does the patient’s anatomy require?
• What treatment result is being sought?

What Is the FDA-Recommended Botox Dose for Glabellar Lines?

For Botox Cosmetic, the current prescribing information recommends:

20 Units total for adult glabellar-line treatment, administered across five injection sites.

That number is specific to onabotulinumtoxinA (Botox Cosmetic). It should not be automatically transferred to another botulinum toxin product.

What Is the FDA-Recommended Letybo Dose for Glabellar Lines?

Letybo is supplied as 50-Unit or 100-Unit single-dose vials.

For its FDA-approved glabellar indication, Letybo’s prescribing information specifies its own dosing and administration instructions.

The important point for patients is that the Letybo dosing system should be followed as Letybo dosing, rather than attempting to translate it into Botox units.

Why Does the Number of Units Matter Less Than You Might Think?

Patients often assume:

More units = stronger treatment = better result. That is not necessarily true. The outcome of a botulinum toxin treatment depends on much more than the numerical dose.

It depends on:

The muscle being treated

Different muscles have different sizes, strengths and functions.

The patient’s anatomy

Facial anatomy varies considerably from person to person.

Injection location

Where the toxin is placed matters.

Treatment objective

A patient wanting subtle softening may need a different approach from someone seeking maximal wrinkle reduction.

Distribution of treatment

The number and location of injection points influence the final result.

Previous treatment

A patient’s response may be influenced by previous botulinum toxin treatments.

Why Doesn’t Everyone Need the Same Dose?

Faces are not standardized.

Two patients may have completely different:

• Corrugator muscle strength
• Procerus activity
• Frontalis activity
• Brow position
• Facial symmetry
• Skin elasticity
• Wrinkle depth
• Expression patterns

Consequently, a treatment plan should not be based solely on a patient’s age or on the number of wrinkles visible in a photograph.

Does Body Size Determine Botox or Letybo Dose?

Not in the same way that it does for many medications.

Botulinum toxin dosing for aesthetic facial treatment is primarily based on the treatment indication, anatomy and muscle activity, rather than simply calculating a dose from total body weight.

A smaller person does not automatically require proportionally less toxin. A larger person does not automatically require proportionally more.

Does the Same Dose Work for Everyone?

No. Clinical trials establish dosing recommendations for specific indications and populations, but individual patients can respond differently.

A patient’s anatomy and muscle activity may make a particular treatment plan more or less appropriate. This is one reason the FDA emphasizes proper dose selection and understanding the relevant neuromuscular and structural anatomy when administering Botox Cosmetic.

Unit count alone does not determine how natural the final result will look. For more on how dosing, anatomy, facial movement, and injection technique influence aesthetic outcomes, see Botox vs. Letybo results and what looks natural.

Why Does Injection Technique Matter?

The toxin does not simply produce an identical effect regardless of where it is injected.

Injection technique involves decisions about:

• Exact location
• Depth
• Distribution
• Number of injection points
• Reconstitution
• Injection volume
• Muscle anatomy

The Botox prescribing information specifically states that safe and effective use depends on proper storage, selection of the correct dose, reconstitution and administration techniques, as well as knowledge of the relevant anatomy.

Is Letybo Stronger Than Botox?

There is no valid way to answer this simply by comparing unit numbers. A product’s numerical unit dose should not be used as a universal “strength” scale.

Clinical studies can compare products when they are appropriately designed to do so.

For example, a randomized Phase III study directly compared Letybo with onabotulinumtoxinA for glabellar lines and found Letybo noninferior for the study’s efficacy endpoint.

That is meaningful evidence. Simply comparing vial numbers is not.

Does More Toxin Mean Better Results?

Not necessarily. The objective of aesthetic botulinum toxin treatment is not to administer the largest possible dose. The objective is to achieve an appropriate clinical and aesthetic effect.

Excessive weakening of muscles can produce unwanted effects, including:

• Excessive reduction in facial movement
• Brow changes
• Eyelid or brow ptosis
• Facial asymmetry
• An appearance the patient considers unnatural

Therefore, “more” should never automatically be equated with “better.”

Using an inappropriate dose or treatment approach can also increase the risk of unwanted effects. For a deeper discussion of potential adverse effects and safety considerations, see Botox vs. Letybo side effects and safety.

Why Is Forehead Dosing Particularly Individualized?

The forehead is a good example of why unit counting alone can be misleading.

The frontalis muscle helps elevate the eyebrows.

If its activity is reduced excessively or in an inappropriate distribution, the appearance of the brow and upper eyelid can change.

This means that forehead treatment requires consideration of:

• Baseline brow position
• Forehead height
• Frontalis strength
• Existing eyelid heaviness
• Brow asymmetry
• Compensatory muscle activity

The FDA-approved Botox Cosmetic labeling specifically identifies the frontalis as the muscle associated with forehead lines and provides indication-specific dosing guidance.

Letybo’s current U.S. FDA-approved cosmetic indication, by contrast, is glabellar lines rather than forehead lines.

Why Should You Be Careful With Online “Unit Conversion” Charts?

Because they can create a false impression of precision.

A chart may say:

20 Botox = X Letybo

But unless that relationship is supported by appropriate product-specific clinical evidence and labeling, the number should not be interpreted as an FDA-established equivalence.

A 2024 review specifically concluded that botulinum toxin units are not interchangeable or convertible using simple dose ratios.

What About Published Studies That Compare Different Botulinum Toxins?

This is where things become more nuanced. Researchers can conduct clinical trials comparing products.

For example, randomized trials have compared different botulinum toxin formulations using specific doses and predefined endpoints.

One Phase III trial of prabotulinumtoxinA versus onabotulinumtoxinA used 20 units of each product for glabellar lines and concluded that prabotulinumtoxinA was noninferior under that study’s design.

That does not mean that all botulinum toxins are universally interchangeable at 20 units.

It means that the specific products and doses tested in that particular clinical trial produced comparable results under those study conditions.

That distinction is extremely important.

So Why Do Doctors Sometimes Discuss “Equivalent” Doses?

Because clinicians and researchers sometimes need to compare products in clinical practice or research. Historically, studies have investigated relative dosing between certain botulinum toxin preparations.

But these comparisons do not create a universal conversion ratio applicable to every toxin, every indication and every patient.

The literature has repeatedly emphasized that botulinum toxin products have product-specific potency and dosing characteristics.

For Letybo specifically, the FDA labeling is particularly clear: its potency units are not interchangeable with other botulinum toxin products.

What Should a Patient Ask Instead of “How Many Units?”

Instead of focusing exclusively on the number, ask:

“Which product are you using?”

“What area are you treating?”

“What result are you trying to achieve?”

“How are you determining my dose?”

“How will you preserve appropriate facial movement?”

“What happens if I need an adjustment?”

These questions provide much more useful information than simply asking whether you are receiving 20, 30 or 50 units.

Does the Injector Matter More Than the Unit Number?

For aesthetic treatment, the unit number is only one component of the treatment plan.

A knowledgeable injector needs to understand:

• Facial anatomy
• Muscle function
• Injection landmarks
• Product-specific labeling
• Dose selection
• Patient expectations
• Potential complications

The Botox prescribing information itself emphasizes the importance of understanding neuromuscular and structural anatomy.

A recent review similarly emphasizes that each botulinum toxin has its own clinical profile and that dosing and injection paradigms should be determined individually for each product and indication.

Dr. Monica Gavin’s Perspective

“I don’t think patients should judge a treatment by the number of units on the syringe. Botox and Letybo use product-specific potency units, so those numbers cannot simply be compared as though they were the same currency. What matters to me is selecting the appropriate product and dose for the patient’s anatomy, the muscle being treated and the result the patient wants.”

— Monica Gavin, MD
Azani Medical Spa
Bethlehem, Pennsylvania

What We Know vs. What We Don’t Know

Botox and Letybo are distinct botulinum toxin products with product-specific potency units.

Their units are not interchangeable. A simple 1:1 conversion is not appropriate. Dosing should follow the product-specific labeling and indication. Patient anatomy and injection technique influence treatment outcomes.

What we should not claim

There is no universal formula establishing that X units of Letybo equal Y units of Botox. A larger numerical dose does not automatically mean a stronger toxin. A smaller numerical dose does not automatically mean a weaker toxin.

Patients should not choose a product simply because the vial contains a smaller or larger number of units.

Botox vs. Letybo Units: The Bottom Line

Letybo units and Botox units are not interchangeable.

There is no scientifically or FDA-established universal conversion that allows patients to say:

“X units of Botox = Y units of Letybo.”

Both products use potency units, but those units are specific to each product’s preparation and assay. For patients, the more meaningful question is not:

“How many units am I getting?”

It is:

“What product is being used, why is this dose appropriate for my anatomy and treatment goal, and how will the treatment be performed safely?”

That is the information that allows a patient to make an informed decision.

Not Sure Whether Botox or Letybo Is Right for You?

Unit numbers alone don’t tell you which treatment is best. At Azani Medical Spa in Bethlehem, PA, Dr. Monica Gavin evaluates your facial anatomy, muscle activity, treatment goals and previous treatment history to develop an individualized plan.

Ready to compare your options?

MEDICAL REFERENCES

U.S. Food and Drug Administration — Letybo Prescribing Information

Current FDA labeling describes Letybo potency units as specific to its preparation and assay and states that they are not interchangeable with other botulinum toxin products.

U.S. Food and Drug Administration — Botox Cosmetic Prescribing Information

FDA labeling describes Botox Cosmetic potency units as product-specific and provides indication-specific dosing recommendations.

Update on Non-Interchangeability of Botulinum Neurotoxin Products

A 2024 review discusses differences among botulinum neurotoxin products and explains why potency units should not be treated as interchangeable or converted using simple dose ratios.

Botulinum Toxin Type A Products Are Not Interchangeable

A peer-reviewed review examining botulinum toxin type A products explains differences in manufacturing, formulation and potency assays and why products should not be treated as interchangeable.

Comparisons Among Botulinum Toxins: An Evidence-Based Review

The literature review concludes that botulinum toxin formulations cannot be reliably converted using a single universal ratio.

PrabotulinumtoxinA vs. OnabotulinumtoxinA Phase III Trial

A randomized Phase III study illustrates an important distinction: products can be directly compared in controlled clinical trials using specific study doses, but this does not create a universal conversion formula applicable to every toxin.