Compounded Tirzepatide: What It Is, How It Works, and What You Need to Know

What compounded tirzepatide is

Compounded tirzepatide is tirzepatide prepared by a compounding pharmacy, physician or outsourcing facility rather than by Eli Lilly, the company that makes the FDA-approved products [3]. Tirzepatide is a dual glucose-dependent insulinotropic polypeptide (GIP) and glucagon-like peptide-1 (GLP-1) receptor agonist, which is how the Zepbound and Mounjaro labels describe it [2][4]. HealthRX.com offers compounded tirzepatide by prescription.

FDA states that compounded drugs are not FDA approved and are not reviewed for safety, effectiveness or quality before they are marketed, and that compounded drugs should only be used in patients whose medical needs cannot be met by an FDA-approved drug [1].

Can pharmacies still compound tirzepatide?

FDA says enforcement discretion ended for state-licensed pharmacies on 2025-03-05 and for outsourcing facilities on 2025-03-19, after a district court denied a preliminary injunction [3].

What remains of the pathway is narrow. A state-licensed pharmacy may compound for an individual patient who has a prescription, but not regularly or in inordinate amounts a product that is essentially a copy of the commercially available drug, unless the prescriber documents a significant difference for that identified patient. FDA says it does not intend to act against a pharmacy that fills four or fewer such prescriptions in a calendar month [3]. Outsourcing facilities generally cannot compound from bulk substances unless the substance appears on the list of bulk drug substances for which there is a clinical need or meets another FDA condition; FDA says tirzepatide does not currently meet those conditions [3].

On 2026-04-30 FDA proposed to exclude semaglutide, tirzepatide and liraglutide from that bulk substances list, finding no clinical need for outsourcing facilities to compound them from bulk substances. Comments were due 2026-06-29, and no final decision was found [6].

How tirzepatide works

The Zepbound label says tirzepatide binds and activates both the GIP and GLP-1 receptors, and that nonclinical studies suggest the added GIP activity may further contribute to regulation of food intake [2]. It decreases calorie intake, stimulates insulin secretion in a glucose-dependent way, reduces glucagon and increases insulin sensitivity [2]. The label also states that tirzepatide lowers body weight with greater fat mass loss than lean mass loss [2].

It delays gastric emptying, with the largest delay after the first dose, diminishing over time [2]. Median time to peak concentration is 24 hours, bioavailability is 80%, half-life is about 5 days, and steady state is reached after 4 weeks of weekly dosing [2].

Whether the extra GIP activity is what makes tirzepatide outperform semaglutide is not settled. In SURMOUNT-5, an open-label trial of 751 adults with obesity and no diabetes, the maximum tolerated dose of tirzepatide lowered weight 20.2% over 72 weeks versus 13.7% with the maximum tolerated dose of semaglutide, and waist circumference fell 18.4 cm versus 13.0 cm [7].

The labeled dosing schedule

The Zepbound label starts at 2.5 mg injected subcutaneously once weekly for 4 weeks, which it calls an initiation dose rather than a maintenance dose, then 5 mg, with increases of 2.5 mg after at least 4 weeks on the current dose. Maintenance doses are 5, 10 or 15 mg weekly for weight reduction and 10 or 15 mg for obstructive sleep apnea, with a maximum of 15 mg [2]. The Mounjaro label starts at 2.5 mg weekly and increases in 2.5 mg steps after at least 4 weeks if more glycemic control is needed, to a maximum of 15 mg weekly in adults and 10 mg in patients aged 10 and older [4]. These labels do not provide instructions for compounded preparations.

What the tirzepatide trials found

SURMOUNT-1 enrolled 2,539 adults with obesity, or overweight plus a weight-related complication, and no diabetes. At 72 weeks, mean weight change was -15.0% on 5 mg, -19.5% on 10 mg and -20.9% on 15 mg versus -3.1% on placebo [5]. At least 20% weight loss occurred in 30.0%, 50.1% and 56.7% of the Zepbound groups, versus 3.1% on placebo [2].

SURMOUNT-2 enrolled 938 adults with type 2 diabetes and a BMI of 27 or higher: -12.8% on 10 mg and -14.7% on 15 mg versus -3.2% on placebo at 72 weeks [8].

SURMOUNT-4: 783 adults took open-label tirzepatide for 36 weeks, and the 670 who were randomized had lost a mean 20.9%; they were then randomized to continue or switch to placebo. From week 36 to week 88, weight changed -5.5% with continued treatment and +14.0% after switching to placebo [9].

These trials did not test compounded preparations, and we found no published trial that reported weight-loss or side-effect rates for compounded tirzepatide itself.

Side effects in the Zepbound label

Pooled placebo-controlled weight trials (up to 72 weeks; 958 people on placebo and 630, 948 and 941 on 5, 10 and 15 mg) reported nausea in 25%, 29% and 28% versus 8% on placebo, diarrhea in 19%, 21% and 23% versus 8%, vomiting in 8%, 11% and 13% versus 2%, and constipation in 17%, 14% and 11% versus 5% [2]. Treatment was stopped for adverse reactions by 4.8%, 6.3% and 6.7% versus 3.4%, and severe gastrointestinal reactions occurred in 1.7%, 2.5% and 3.1% versus 1% [2]. Hair loss was reported by 5%, 4% and 5% versus 1%, and was more frequent in women: 7.1% of women versus 0.5% of men on Zepbound [2].

The label's warnings include acute pancreatitis (discontinue if suspected; adjudicated cases 0.2% versus 0.2% in the pooled weight trials, and 0.84 versus 0 per 100 patient-years in the sleep apnea studies), acute gallbladder disease (cholecystitis 0.7% versus 0.2%), acute kidney injury from volume depletion, hypoglycemia that is more likely with insulin or a sulfonylurea, serious hypersensitivity, diabetic retinopathy complications, and pulmonary aspiration during general anesthesia or deep sedation [2]. Mean resting heart rate rose 1 to 3 beats per minute [2].

The boxed warning covers thyroid C-cell tumors seen in rats, with human relevance unknown; tirzepatide is contraindicated with a personal or family history of medullary thyroid carcinoma or MEN 2 [2]. The label advises discontinuing Zepbound when pregnancy is recognized, and advises people using oral hormonal contraceptives to switch to a non-oral method or add a barrier method for 4 weeks after starting and for 4 weeks after each dose escalation [2].

What FDA says about the vial

FDA notes that compounded GLP-1 drugs are often dispensed in vials containing multiple doses. It recommends discarding such a vial 28 days after first use even if medication remains, even if the compounder's instructions say otherwise, and using a new sterile needle and syringe for every dose [1]. It also recommends not using an injectable GLP-1 drug that arrives warm or with inadequate ice packs, because storage temperature can affect quality [1]. As of 2026-05-31, FDA had received more than 730 adverse event reports for compounded tirzepatide and says that number likely undercounts [1].

What has been published about compounded tirzepatide

Published work on compounded tirzepatide is thin. Testing of compounded products that combine tirzepatide with vitamin B12 analogs found a widespread, previously unidentified impurity, formed by a chemical reaction between tirzepatide and certain B12 analogs; the clinical effects of that impurity are unknown [10].