FDA Safety Alert
The FDA has received reports of patients mistakenly injecting 5 to 20 times more than their prescribed dose from multi-dose vials. Some patients required hospitalization for severe nausea, vomiting, acute pancreatitis, and gallstones. Always verify your dose calculation before injecting.
Unlike FDA-approved Wegovy and Ozempic that come in pre-filled pens with preset doses, compounded semaglutide typically comes in multi-dose vials. This means you're responsible for drawing up the correct amount using a syringe—and the math can be confusing.
Why Dosing Errors Happen
The primary source of confusion is the difference between how doses are prescribed versus how vials are labeled:
- • Prescriptions are written in milligrams (mg) — for example, "0.25 mg weekly"
- • Syringes measure in milliliters (mL) or units — you need to calculate how many mL equals your mg dose
- • Vials come in various concentrations — a 5 mg/2 mL vial is very different from a 10 mg/2 mL vial
Patients often use insulin syringes (labeled in "units") to draw their doses, which adds another layer of conversion. And different compounders use different vial concentrations, making it impossible to give universal volume instructions.
Understanding Concentration: The Key Concept
Every compounded semaglutide vial has a concentration listed on the label. This tells you how many milligrams of medication are dissolved in each milliliter of liquid.
Common Concentration Examples:
5 mg/2 mL vial
= 2.5 mg per mL (or 0.25 mg per 0.1 mL)
10 mg/2 mL vial
= 5 mg per mL (or 0.5 mg per 0.1 mL)
2.5 mg/mL vial
= 0.25 mg per 0.1 mL
Step-by-Step Dose Calculation
Follow this process every time you draw a dose. Write it down until you're confident in the math.
Find Your Vial's Concentration
Look at your vial label. It will say something like "Semaglutide 5 mg/2 mL" or "2.5 mg/mL". Write this down.
Calculate mg per mL
If your vial says 5 mg/2 mL, divide: 5 ÷ 2 = 2.5 mg per mL
Calculate Your Volume
Divide your prescribed dose by the concentration.
Example: If prescribed 0.5 mg and your concentration is 2.5 mg/mL:
0.5 mg ÷ 2.5 mg/mL = 0.2 mL
Convert to Syringe Units (if needed)
If using a U-100 insulin syringe, remember: 100 units = 1 mL
So 0.2 mL = 20 units on a U-100 syringe
Real-World Calculation Examples
Example 1: Starting Dose
Prescribed: 0.25 mg weekly
Vial concentration: 5 mg/2 mL (= 2.5 mg/mL)
Calculation: 0.25 mg ÷ 2.5 mg/mL = 0.1 mL
On U-100 syringe: Draw to the 10-unit mark
Example 2: Maintenance Dose
Prescribed: 1 mg weekly
Vial concentration: 10 mg/2 mL (= 5 mg/mL)
Calculation: 1 mg ÷ 5 mg/mL = 0.2 mL
On U-100 syringe: Draw to the 20-unit mark
Example 3: Higher Dose
Prescribed: 2.4 mg weekly
Vial concentration: 10 mg/2 mL (= 5 mg/mL)
Calculation: 2.4 mg ÷ 5 mg/mL = 0.48 mL
On U-100 syringe: Draw to the 48-unit mark
Common Mistakes That Cause Overdoses
Mistake #1: Confusing units with mL
If prescribed "5 units" and you draw 5 mL instead, you've injected 100 times more than intended.
Mistake #2: Using the wrong syringe
Different syringe types have different scales. A 3 mL syringe reads differently than a U-100 insulin syringe.
Mistake #3: Not recalculating for new vials
If your pharmacy changes vial concentrations, your volume changes too. Always check the label.
Mistake #4: Drawing the full vial
Multi-dose vials contain multiple weeks' worth of medication. Never inject the entire vial contents at once.
Safety Checklist Before Every Injection
- ☐ Verified the vial concentration matches what I expected
- ☐ Calculated my volume in mL (prescribed mg ÷ concentration)
- ☐ Converted mL to units if using an insulin syringe (mL × 100 = units)
- ☐ Double-checked my math (or had someone else verify)
- ☐ Used the correct syringe type for my calculation
- ☐ The amount I'm drawing is a small fraction of the total vial
What If You Accidentally Overdose?
If you believe you've injected more than your prescribed dose:
- 1 Don't panic — but take it seriously
- 2 Contact your provider immediately or call Poison Control at 1-800-222-1222
- 3 Monitor for symptoms — severe nausea, vomiting, abdominal pain, low blood sugar
- 4 Go to the ER if you experience: severe symptoms, signs of low blood sugar, or inability to keep fluids down
- 5 Stay hydrated if you can tolerate fluids
Ask Your Provider for Help
A reputable telehealth provider should be able to answer these questions before you start treatment:
- • What concentration vial will I receive?
- • What type of syringe should I use?
- • How many units/mL should I draw for my prescribed dose?
- • Can you provide written dosing instructions specific to my vial?
- • Who do I contact if I have dosing questions?
If a provider can't or won't answer these questions clearly, consider that a red flag. Your safety depends on understanding exactly how to dose your medication correctly.
Find Providers with Clear Dosing Support
Compare telehealth providers that offer comprehensive dosing instructions and patient support. Some use prefilled syringes to eliminate dosing calculations entirely.
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