Understanding Medication Dosage: Concentration, Quantity, and Units Injected

by | May 9, 2024

For many patients participating in medical weight loss programs, managing their medication can sometimes be confusing, especially when it comes to understanding the differences between concentration, quantity, and units injected. To ensure safety and effectiveness, it’s helpful to have a clear understanding of these terms. 

Please note the dose of your medication will be labeled. This blog is a deep dive into understanding the numbers involved. This is not a math test! If you have any questions about your dosing, please reach out to your clinician.

What is Concentration?

The concentration of a medication refers to the amount of the drug contained in a specific volume of liquid. It is expressed in milligrams per milliliter (mg/ml). For example, Semaglutide is often labeled as 2.5 mg/ml, this means that each milliliter of the liquid contains 2.5 milligrams of the active substance. Understanding the concentration is crucial as it determines the dosage of the drug that a patient receives per injection, ensuring the effectiveness of the treatment while minimizing the risk of overdose.

If the medication is compounded with Vitamin B12 or another medication, the concentration will be reported as two milligram amounts per ml.  For example: Tirzepatide/Cyanocobalamin: 2.5mg/1mg/0.5mL. This means each 0.5 ml (50 units) contains 2.5 mg of Tirzepatide and 1 ml of Cyanocobalamin. Cyanocobalamin is a form of Vitamin B12.

What is Quantity?

The quantity of a vial refers to the total volume of liquid inside the vial, which is typically expressed in milliliters (ml). For instance, if you have a vial labeled as 3 ml, it contains three milliliters of the medication. This measurement tells you how much total liquid is available for use. Weight loss medication vials typically contain one month’s worth of medication. Video on how to get the final amounts of medication out of the vial.

Please note that some pharmacies use a large vial size (Hallandale, Empower) and other pharmacies use smaller vial sizes (Striker, South End). This does not change the quantity (in milliliters) of the medication.

What are Units Injected?

The units injected refer to the actual amount of medication administered with each injection. The syringes you receive are measured in units.  100 units equals 1 milliter (ml). Some syringes go up to 30 units, meaning they contain up to 0.3 ml.  Other syringes go up to 50 units (0.5 ml) or 100 units (1 ml).

Common dosing

Semaglutide typically comes in 1, 2, or 3ml vials. The concentration of Hallandale and PQ Semaglutide is 2.5 mg/ml.  A starting dose is usually 10 or 15 units.  10 units = 0.1 ml.  Since the concentration is 2.5 ml/ml this means the starting dose is 0.25 mg.  The maximum dose of Semaglutide is 2.4 mg.  This equals 96 units.

Of note, Empower Pharmacy makes a more concentrated form of Semaglutide which is labeled as 5 mg / 0.5 ml.  To make things more simply we convert to 1 ml:  5 mg / 0.5 ml equals 10 mg / 1 ml.  The max dose of 2.4 mg equals 24 units of this more concentrated medication.

Tirzepatide has different concentrations based on the pharmacy. Striker Pharmacy adjusts the concentration to the mg dose so the injected amount is always 50 units.  The starting dosage of Tirzepatide is 2.5 mg weekly.  They use a concentration of 2.5 mg / 0.5 ml for this dose.  This equals a 50 unit injection.  At higher dosing, they change the concentration.

Other forms of Tirzepatide (Hallandale and PQ) use a standard concentration of 10 mg / 1 ml (also reported as 5 mg / 0.5 ml). For a starting dose of 2.5 mg, this equals 25 units. At higher dosing (10 mg weekly and greater) we recommend using a more concentrated medication since the amount injected would be two shots.  The maximum syringe size is 100 units (1 ml).

Why is the Medication Red-Colored?

The red color is due to the compounded Vitamin B12.

Putting It All Together

To illustrate, imagine you are prescribed a medication with a concentration of 2.5 mg/ 0.5 ml in a 2 ml vial. This is a standard starting dose of Tirzepatide from Striker Pharmacy.  For a 2.5 mg dose, you would inject 0.5 ml which is 50 units.  Your vial size is 2 ml (200 units) which contains 4 doses. 

Understanding these terms not only helps in accurately administering your medication but also empowers you to engage more actively in your treatment plan. If you ever find yourself confused or unsure about how to measure your dose, do not hesitate to ask your healthcare provider for clarification. Remember, managing your medication correctly is a key component of your journey to successful weight loss.

This blog post is intended for educational purposes only and should not be considered a substitute for professional medical advice.


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