How many injections can be obtained from a 12 mg vial of retatrutide (generic name) if 0.2 mL is withdrawn for each injection?

Calculating Injections from a 12 mg Vial

You cannot determine the number of injections from a 12 mg vial using only a 0.2 mL withdrawal volume—you must know the concentration (mg/mL) of the vial.

The Critical Missing Information

The calculation requires the vial's concentration, which is not provided in your question. Here's why this matters:

• A 12 mg vial could have different concentrations depending on the total volume of liquid in the vial 1
• The same dose can be delivered in different volumes by adjusting concentration (e.g., 0.05 mL of a 1:1 solution equals 0.5 mL of a 1:10 solution) 1

How to Calculate Once You Know the Concentration

Step 1: Determine the vial concentration

• Check the vial label for concentration expressed as mg/mL or as a ratio (e.g., 1:100 wt/vol) 1

Step 2: Calculate dose per injection

• Dose per injection (mg) = Concentration (mg/mL) × Volume withdrawn (mL) 1
• In your case: Dose per injection = Concentration × 0.2 mL

Step 3: Calculate number of injections

• Number of injections = Total vial content (12 mg) ÷ Dose per injection (mg) 1

Practical Example Scenarios

If the vial concentration is 10 mg/mL:

• Dose per 0.2 mL = 10 mg/mL × 0.2 mL = 2 mg per injection
• Number of injections = 12 mg ÷ 2 mg = 6 injections 1

If the vial concentration is 6 mg/mL:

• Dose per 0.2 mL = 6 mg/mL × 0.2 mL = 1.2 mg per injection
• Number of injections = 12 mg ÷ 1.2 mg = 10 injections 1

If the vial concentration is 20 mg/mL:

• Dose per 0.2 mL = 20 mg/mL × 0.2 mL = 4 mg per injection
• Number of injections = 12 mg ÷ 4 mg = 3 injections 1

Common Pitfalls to Avoid

• Never assume the total vial volume equals 1 mL just because the total drug content is 12 mg—the vial could contain 0.6 mL, 1.2 mL, 2 mL, or any other volume 1
• Do not confuse total drug content (mg) with concentration (mg/mL)—these are fundamentally different measurements 1
• Always verify the concentration on the vial label before calculating doses, as medication errors from concentration miscalculations can be dangerous 1

For Retatrutide Specifically

Based on the phase 2 trial data, retatrutide was administered as subcutaneous injections with doses ranging from 0.5 mg to 12 mg weekly 2, 3. However, the specific concentration formulation used in these trials is not disclosed in the available evidence. You must obtain the concentration information from your specific vial's labeling to perform this calculation accurately.