Tirzepatide/B12

Common questions about Tirzepatide/B12

What is Tirzepatide/B12 from PeptideRx?

Tirzepatide/B12 is a compounded injectable that pairs tirzepatide, a dual GIP and GLP-1 receptor agonist, with cyanocobalamin (vitamin B12). Tirzepatide is the same active ingredient as Mounjaro and Zepbound. The compound is dispensed by Optimal Balance Pharmacy under a 503A patient-specific prescription. Every batch is tested by Eagle Analytical Services for sterility and bacterial endotoxin (USP <85>); the Certificate of Analysis is published on this page. Vial sizes range from a 12 mg starter at $45 to a 180 mg vial at $675, with a flat $39 medical visit fee.

Does compounded tirzepatide work the same as Mounjaro or Zepbound?

Compounded tirzepatide uses the same active ingredient as Mounjaro and Zepbound: tirzepatide. The dose-response and mechanism are identical because the molecule is the same. The compounded version Optimal Balance Pharmacy dispenses is co-formulated with cyanocobalamin (B12), which is pharmacologically inert with respect to weight loss; the B12 supports energy levels during caloric deficit but does not change tirzepatide's pharmacology. The pivotal SURMOUNT-1 trial showed 15 to 22 percent mean body weight loss over 72 weeks at therapeutic doses; that data applies because the active molecule is identical. The PeptideRx protocol does use a different dosing schedule than branded Mounjaro (1.5 mg twice weekly versus 2.5 mg once weekly); see the next question for why.

What is the starting dose of compounded tirzepatide at PeptideRx?

The PeptideRx starting protocol is 25 units (1.5 mg) on a U-100 insulin syringe, taken subcutaneously twice weekly, for a total of 3 mg per week. Branded Mounjaro and Zepbound use 2.5 mg once weekly per Lilly's prescribing information. The split-dose protocol used by many compounding telehealth clinics is intended to smooth the Cmax peak that drives nausea: tirzepatide has a roughly 120-hour half-life (StatPearls pharmacokinetics) and once-weekly dosing produces a peak 8 to 72 hours post-injection where GI side effects cluster. Splitting the dose flattens the AUC curve and lowers that peak. Pharmacokinetic modeling and clinical experience support this approach, though no head-to-head randomized trial has compared 1.5 mg twice weekly versus 2.5 mg once weekly. Your provider may adjust based on your medical history, GLP-1 treatment history, and side-effect tolerance.

How does PeptideRx's twice-weekly protocol compare to Mounjaro's once-weekly schedule, and how do the units work?

On the PeptideRx protocol, the starting dose is 25 units (1.5 mg) twice weekly drawn from a 6 mg/mL starter vial; 25 units equals 0.25 mL on a U-100 insulin syringe. For reference, the branded Mounjaro 2.5 mg once-weekly equivalent on a 6 mg/mL vial would be approximately 42 units (0.42 mL), but that schedule is not the PeptideRx protocol. Always verify the concentration printed on your specific vial before drawing, because Optimal Balance Pharmacy ships multiple concentrations across the titration ladder and the unit-to-mg ratio changes with each strength. Your shipment includes a per-vial unit conversion table for safety.

Why is the compounded tirzepatide co-formulated with cyanocobalamin (B12)?

Cyanocobalamin is a soluble carrier that doubles as an energy-supporting cofactor for patients in caloric deficit. B12 supports red blood cell production and methylation pathways that come under load during rapid fat loss. The 0.5 mg/mL inclusion is well below any clinical toxicity threshold and has no effect on tirzepatide's GIP or GLP-1 receptor binding. The B12 carrier is a formulation choice by Optimal Balance Pharmacy, not by PeptideRx; PeptideRx is the prescribing source. Patients with documented B12 sensitivity or MTHFR methylation variants should ask their provider about the Tirzepatide/Glycine variant instead.

Where do I inject tirzepatide?

Tirzepatide is injected subcutaneously into the abdomen, the upper outer thigh, or the back of the upper arm. Rotate sites with each injection. Avoid the same location within a 1-inch radius of any prior injection in the past 7 days. The needle should be 31-gauge and 5/16-inch (8 mm) on a U-100 insulin syringe (included with every PeptideRx order). Pinch the skin and inject at a 90-degree angle. For step-by-step technique, see the PeptideRx injection guide.

Does tirzepatide cause hair loss?

Hair loss is reported in approximately 5 percent of tirzepatide users in clinical trial data. The mechanism is generally telogen effluvium driven by rapid weight loss rather than a direct effect of tirzepatide, similar to what is seen after bariatric surgery or any aggressive caloric deficit. Most cases are temporary and resolve within 3 to 6 months once weight stabilizes. Adequate protein intake (at least 1 gram per kilogram of body weight per day) and complete-vitamin coverage reduce risk.

Does tirzepatide make you tired?

Fatigue is a documented side effect of tirzepatide, particularly during the first 4 to 6 weeks of titration. The cause is multifactorial: reduced caloric intake, slower gastric emptying, mild dehydration if water intake drops with appetite, and elevated B12 demand during a rapid metabolic shift. The B12 in the Optimal Balance Pharmacy formulation directly addresses the last factor. If fatigue persists beyond 6 weeks, message your provider through the dashboard for a protocol review.

How long does tirzepatide last in the fridge once opened?

Compounded tirzepatide vials carry a Beyond Use Date (BUD) of up to 120 days from compounding under USP <797> sterile compounding standards. The BUD is printed on every vial label by Optimal Balance Pharmacy. Refrigerate unopened vials at 36 to 46 degrees Fahrenheit. Once a vial is punctured for first use, follow the in-use BUD printed on your specific label (typically 28 days at refrigerator temperature). Do not freeze.

Is tirzepatide better than semaglutide for weight loss?

Tirzepatide and semaglutide have both been studied in pivotal trials for weight loss. The SURMOUNT-1 trial reported 15 to 22 percent mean body weight loss on tirzepatide over 72 weeks; the STEP-1 trial reported approximately 14.9 percent on semaglutide over 68 weeks. Tirzepatide's dual GIP and GLP-1 receptor activation typically produces stronger appetite suppression than semaglutide's GLP-1-only mechanism. Semaglutide is often preferred for patients with milder weight-loss goals or histories of severe GI side effects, because tirzepatide tends to produce stronger nausea during titration. Your PeptideRx provider will recommend based on your medical history.