Tirzepatide Dosage Calculator

Tirzepatide is a novel dual glucose-dependent insulinotropic polypeptide (GIP) and glucagon-like peptide-1 (GLP-1) receptor agonist developed by Eli Lilly. It is a 39-amino acid synthetic peptide with a C20 fatty diacid moiety enabling weekly dosing via extended albumin binding. Marketed as Mounjaro for type 2 diabetes management and Zepbound for chronic weight management, tirzepatide represents the first approved incretin-based therapy to simultaneously target both the GLP-1 and GIP receptor pathways, producing synergistic metabolic effects that surpass those seen with GLP-1 monotherapy agents.

In the landmark SURPASS clinical trial program, tirzepatide at 15 mg per week produced mean HbA1c reductions of up to 2.58 percentage points in people with type 2 diabetes. In the SURMOUNT program for obesity research, participants receiving 15 mg per week achieved mean body weight reductions of 22.5% over 72 weeks, a magnitude of weight loss previously only observed with bariatric surgery in controlled trial settings. These results have driven intense scientific interest in the compound's mechanisms and potential applications beyond glycemic control.

Tirzepatide activates both the GIP receptor and the GLP-1 receptor as a "twincretin," though it functions as a full agonist at the GIP receptor and a partial agonist at the GLP-1 receptor, with binding properties distinct from endogenous GLP-1. The GIP receptor is expressed in pancreatic beta cells, adipose tissue, bone, and the brain; activation enhances glucose-stimulated insulin secretion and, importantly, may reduce the nausea and emesis commonly associated with pure GLP-1 agonism — potentially explaining the improved tolerability profile observed in some clinical comparisons.

Combined GIP and GLP-1 receptor co-agonism produces complementary effects on energy homeostasis: enhanced insulin secretion, glucagon suppression, slowed gastric emptying, increased satiety, and potentially direct effects on adipose tissue lipolysis and fatty acid oxidation. Preclinical data suggest tirzepatide may reduce hepatic fat accumulation and improve markers of non-alcoholic fatty liver disease, an area of active clinical investigation.

Tirzepatide lyophilized powder is reconstituted with bacteriostatic water for injection. For a 5 mg vial, inject 1 mL of bacteriostatic water slowly against the inner glass wall of the vial using a sterile syringe. Allow the vial to rest for 60 seconds, then swirl gently until the powder fully dissolves. The reconstituted solution should be clear and colorless to pale yellow. Do not shake the vial. For a 10 mg vial, 1 mL reconstitution yields 10,000 mcg/mL; using 2 mL yields 5,000 mcg/mL.

Because tirzepatide doses are expressed in milligrams (not micrograms), use caution when converting: 2.5 mg = 2,500 mcg, 5 mg = 5,000 mcg. The calculator above works in micrograms — enter your dose in mcg accordingly. Use U100 insulin syringes (27–30 gauge) for subcutaneous administration.

The SURPASS and SURMOUNT trial programs established a standardized escalation schedule for tirzepatide to improve tolerability. The typical protocol begins at 2.5 mg per week for the first four weeks, then increases by 2.5 mg every four weeks until reaching the target maintenance dose: 5 mg, 7.5 mg, 10 mg, 12.5 mg, or 15 mg weekly. The maximum studied dose in clinical trials is 15 mg per week.

In diabetes outcome studies (SURPASS), 5 mg, 10 mg, and 15 mg doses were compared; all three showed statistically significant HbA1c reductions versus comparators including insulin degludec, insulin glargine, and semaglutide 1 mg. In SURMOUNT-1, both the 10 mg and 15 mg maintenance doses produced weight loss exceeding 20% at 72 weeks in subjects without diabetes.

Using the calculator: a 10 mg vial reconstituted with 1 mL of bacteriostatic water yields 10,000 mcg/mL. A 2.5 mg (2,500 mcg) initiation dose requires 0.25 mL (25 IU on a U100 syringe). A 15 mg (15,000 mcg) maintenance dose from a 10 mg vial reconstituted with 1 mL would require 1.5 mL — exceeding a single vial, so two vials may be needed at high doses.

Lyophilized tirzepatide powder should be refrigerated at 2–8°C and protected from light. Do not freeze. Once reconstituted in bacteriostatic water, store the vial at 2–8°C and use within 28 days. Tirzepatide solutions should not be exposed to temperatures above 30°C for extended periods. Always inspect the solution before drawing your dose — discard any vial showing cloudiness, visible particles, or unusual color. Label each vial with the reconstitution date. Transport reconstituted vials in an insulated cooler with ice packs; avoid direct contact between the vial and ice to prevent localized freezing.

Gastrointestinal adverse effects — nausea, diarrhea, vomiting, and decreased appetite — are the most commonly reported events in tirzepatide trials, occurring predominantly during dose escalation and diminishing with continued use. Compared to semaglutide 1 mg in the SURPASS-2 head-to-head trial, tirzepatide 5, 10, and 15 mg demonstrated higher rates of nausea but also greater HbA1c and weight reduction. Rare but serious adverse events include acute pancreatitis, cholelithiasis, and hypoglycemia when combined with insulin or sulfonylureas. Thyroid C-cell effects observed in rodent models necessitate caution in subjects with a history of medullary thyroid carcinoma or MEN2. This is a research chemical intended for laboratory use only.