GLP-1 Split Dose Calculator
Split a weekly semaglutide or tirzepatide dose into smaller injections
Enter your total weekly dose and choose a split schedule to estimate the amount per injection and a sample calendar.
Split Dose Calculator
How to Use This Calculator
Enter your weekly dose
Use the total weekly amount your prescriber recommended (mg per 7 days).
Pick a split schedule
Choose twice weekly or a consistent "every few days" plan.
Select your injection days
For twice weekly, pick two days (e.g., Monday and Thursday). For every few days, choose your interval.
Review your split dose
We'll show your dose per injection and a calendar. Confirm your plan with your clinician.
Frequently Asked Questions
Common questions about split dosing for GLP-1 medications.
What is split dosing?
Split dosing means dividing a weekly medication amount into smaller injections taken more frequently than once per week. For example, instead of 10 mg once weekly, you might take 5 mg twice weekly.
Is split dosing FDA-approved for semaglutide or tirzepatide?
No. FDA labeling for these products describes once-weekly injection. Split dosing may be used off-label under clinician guidance, but it was not the regimen studied in pivotal trials like STEP-1 (semaglutide) and SURMOUNT-1 (tirzepatide).
How does the calculator compute my dose per injection?
For "every X days," it uses: Dose = weekly dose × (X/7). For "twice weekly," each dose is proportional to the interval it covers. For example, with Monday/Thursday (3 days then 4 days), Monday's dose = weekly × (3/7) and Thursday's dose = weekly × (4/7). This maintains a consistent mg/day rate across the week.
Why are my two doses different amounts?
With twice-weekly dosing, your two injection days are usually not evenly spaced (e.g., 3 days then 4 days). We calculate each dose proportionally so the day with a longer interval until your next injection gets a larger dose. This approach maintains a more consistent daily medication delivery rate. The total weekly dose remains the same.
Does split dosing change my total weekly dose?
If you follow the calculator's schedule, the average weekly total stays the same. The tool is converting timing, not increasing the intended weekly amount.
Why might someone consider split dosing?
Some people seek steadier medication levels across the week. Because these drugs have long half-lives (semaglutide ~1 week; tirzepatide ~5-6 days), the time between injections affects how much levels rise and fall. Important: this is not a guarantee of fewer side effects or better efficacy.
Can I do this with brand pens like Wegovy, Ozempic, Zepbound, or Mounjaro?
Many products are designed for specific dosing presentations (single-dose pens or multi-dose pens). Do not modify devices or transfer medication. If you use a vial/syringe, get proper training—FDA has reported dosing errors with compounded semaglutide, often due to confusion between mg, mL, and "units."
Does this replace medical advice?
No. This tool is informational. Always verify dosing and timing with your prescriber or pharmacist. Split dosing decisions should be made in consultation with a healthcare provider who knows your full medical history.
Data Sources
Calculation methodology and safety information based on the following sources:
- Wegovy Prescribing Information (Novo Nordisk) — Once-weekly dosing guidance, allowed spacing when changing injection day (≥2 days), and semaglutide half-life ≈ 1 week
- Zepbound Prescribing Information (Eli Lilly) — Once-weekly dosing guidance, spacing when changing administration day (≥3 days), and tirzepatide half-life ≈ 5-6 days
- STEP-1 Trial (NEJM 2021) — Pivotal obesity trial confirming once-weekly semaglutide 2.4 mg regimen
- SURMOUNT-1 Trial (NEJM 2022) — Pivotal obesity trial confirming once-weekly tirzepatide regimen
- FDA Safety Alert (2024) — Dosing errors with compounded semaglutide — warnings about vial/syringe measurement errors and unit confusion
- Ikushima et al. (2018, PMC) — Semaglutide PK — supporting the concept that ~1-week half-life aligns with weekly dosing
- Cengiz et al. (2025, Diabetes Obesity & Metabolism) — Nonstandard dosing regimens explored via modeling — confirms clinical trials used weekly dosing
⚠️ Important Medical Disclaimer
This calculator is for informational purposes only and does not constitute medical advice. Always consult with your healthcare provider before making any changes to your medication dosing.
Dosage calculations should be verified by a healthcare professional. Glapp and its contributors assume no liability for medication dosing errors or adverse events.
Off-Label Use Notice: Split dosing features represent off-label use not approved by the FDA. Discuss with your prescriber before implementing.