Tirzepatide (20 mg Vial) Dosage Protocol
Tirzepatide is a dual GLP-1/GIP receptor agonist studied for type-2 diabetes and chronic weight management. SURMOUNT-1 reported up to 22.5% body-weight reduction at the 15 mg weekly dose. This page covers the 20 mg vial.
⚡ Quickstart Highlights
Dosing & Reconstitution Guide
Route: Subcutaneous | Frequency: Once weekly | Half-life: ~5 days
Standard Approach (3 mL = 6.67 mg/mL)
Reconstituting with 3 mL bacteriostatic water produces a concentration of 6.67 mg/mL. Volume per dose changes with concentration; mg dose itself does not change between vial sizes.
| Phase / Protocol | Dose | U-100 Units | Volume | Doses per vial |
|---|---|---|---|---|
| Weeks 1–4 (titration) | 2.5 mg | 37.5 units | 0.38 mL | 8 doses |
| Weeks 5–8 | 5 mg | 75 units | 0.75 mL | 4 doses |
| Weeks 9–12 | 7.5 mg | 112.5 units | 1.12 mL | 2 doses |
| Weeks 13–16 | 10 mg | 150 units | 1.50 mL | 2 doses |
| Weeks 17–20 | 12.5 mg | 187.5 units | 1.88 mL | 1 doses |
| Weeks 21+ (maintenance) | 15 mg | 225 units | 2.25 mL | 1 doses |
Reconstitution Steps
- Wipe the vial stopper and BAC water vial with alcohol; let dry.
- Draw 3 mL of bacteriostatic water into a sterile syringe.
- Inject slowly down the inside glass wall of the peptide vial. Do not aim at the powder.
- Gently swirl until fully dissolved. Do not shake.
- Label with reconstitution date. Refrigerate at 2–8°C; use within 28 days.
Supplies Needed
Estimates for an 8-week and 12-week cycle at 15 mg per dose, once weekly (1 dose/week).
| Item | 8-Week Cycle | 12-Week Cycle |
|---|---|---|
| Tirzepatide (20 mg) vials | 8 vials | 12 vials |
| Insulin syringes (U-100) | 8 | 12 |
| Bacteriostatic water (10 mL) | 3 × 10 mL | 4 × 10 mL |
| Alcohol swabs | 1 × 100-pack | 2 × 100-pack |
Protocol Overview
Tirzepatide protocols mirror the SURMOUNT-1 trial design — a 5-step titration over 20 weeks, with 4-week intervals between escalations. The dual GLP-1/GIP mechanism produces faster initial weight loss than single-agonist GLP-1s, with most users feeling appetite suppression by week 1.
Most trial subjects reach 15 mg maintenance by week 21 and continue indefinitely. Real-world protocols sometimes top out earlier (10 or 12.5 mg) if the appetite-suppression effect at lower doses is sufficient and the user wants to minimize side-effect burden.
Cycle length: SURMOUNT-1 ran 72 weeks of continuous use with 20.9% mean weight loss. Most research protocols run 6–18 months. Maintenance dosing after target weight is common — reducing to a weekly 5 or 7.5 mg dose to maintain results without continuing to lose.
What to expect by week: Weeks 1–4 — appetite suppression begins, mild-moderate nausea. Weeks 5–12 — steady weight loss curve, side effects diminish. Weeks 13–24 — most users reach 50–70% of target. Weeks 24+ — gradual continued loss; consider whether to reach max dose or stay at intermediate.
Dosing Protocol
The SURMOUNT-1 titration protocol — used in obesity trials — escalates every 4 weeks:
- Weeks 1–4: 2.5 mg once weekly. Tolerability assessment dose.
- Weeks 5–8: 5.0 mg once weekly. First therapeutic step.
- Weeks 9–12: 7.5 mg once weekly.
- Weeks 13–16: 10.0 mg once weekly. Many users plateau here for 4–8 weeks before deciding whether to escalate.
- Weeks 17–20: 12.5 mg once weekly.
- Weeks 21+ (maintenance): 15.0 mg once weekly. SURMOUNT-1 maintenance dose.
SURPASS protocol (T2DM): Same titration, with maintenance often at 5, 10, or 15 mg depending on glycemic targets.
Lower-maintenance protocols: Some research protocols cap at 10 or 12.5 mg long-term — both produced significant weight loss in trials with fewer side effects than 15 mg.
Day-of-week timing: Same day each week. Half-life ~5 days. Most users dose Sunday or Monday so peak effect coincides with weekday meals.
Missed dose: ≤72h late, take when remembered. >72h, skip and resume next scheduled day.
Plateau approach: If weight loss stalls for 4+ weeks at a given step, consider escalating to the next step. If side effects are limiting, stay put and let the body adjust.
Storage Instructions
| State | Temperature | Duration |
|---|---|---|
| Lyophilized | −20°C (−4°F) | Up to 24 months, dry & dark |
| Reconstituted | 2–8°C (35–46°F) | Up to 28 days, protect from light |
Important Notes
How This Works
Tirzepatide is a 39-amino-acid synthetic peptide that activates both GLP-1 and GIP receptors with a single molecule. GLP-1 activation slows gastric emptying, increases satiety, and stimulates glucose-dependent insulin secretion. GIP activation augments insulin secretion further and modulates fat-cell metabolism.
The molecule is fatty-acid acylated to bind albumin and persist in circulation for once-weekly dosing.
Potential Benefits & Side Effects
Potential Benefits
- SURMOUNT-1: 20.9% weight reduction at 15 mg weekly over 72 weeks vs 3.1% placebo.
- SURPASS-2 (T2DM): HbA1c reduction up to 2.46% at 15 mg.
- Greater outcomes than single-agonist comparators in head-to-head trials.
- Improvement in lipid profile and waist circumference reported alongside weight loss.
Side Effect Profile
- Nausea (most common, dose-dependent).
- Diarrhea and vomiting (more common at higher doses).
- Decreased appetite (intended effect).
- Constipation in some users.
- Rare: pancreatitis, gallbladder events.
Lifestyle Factors
- Aggressive hydration — incretin agonists blunt thirst sensation.
- Protein 1.0–1.6 g/kg/day preserves lean mass during weight loss.
- Resistance training 2–3×/week mitigates muscle loss in caloric deficit.
- Avoid high-fat or large-volume meals around dosing.
- Pace meals slowly; eat to 80% fullness rather than past it.
Injection Technique
- Inject subcutaneously into abdomen (away from navel), outer thigh, or upper arm.
- Rotate sites with each weekly dose.
- 90° angle with short insulin needles (4–8 mm).
- Bring vial to room temperature 15 min before injecting.
- Hold 5 seconds after full plunger depression before withdrawing.