TL;DR: Research-grade tirzepatide (4,813 Da, dual GIP/GLP-1 agonist) drops below $3/mg in 60mg vials in 2026 — roughly $60-140/month at 2.5-5 mg/week from research vendors, vs $200-500/month for compounded pharmacy product. SURMOUNT-1 showed 22.5% body weight reduction.

Tirzepatide is the most effective weight-loss peptide with a published Phase 3 trial — SURMOUNT-1 showed up to 22.5% body weight reduction. It’s also the most popular research peptide on the market, which means vendor quality varies wildly. A cheap 30mg vial from the wrong source can contain 60% of the labeled dose, or worse, be a different compound entirely.

This guide covers what you should actually pay per milligram, which vial size fits a titration protocol, how to verify a COA for a complex modified peptide, and the vendor red flags that signal counterfeit product. Tirzepatide is a 39-amino-acid dual GIP/GLP-1 agonist with a C20 fatty-acid side chain — synthesis is non-trivial, and quality matters.

This is not a ranked vendor list — for that, see our Best Tirzepatide Vendors comparison. This guide teaches you how to evaluate any vendor yourself.

Understanding Tirzepatide Pricing

Tirzepatide is sold as a lyophilized powder in sealed glass vials. The three factors that move price: vial size (bigger = substantially cheaper per mg), manufacturer sourcing (US-synthesized costs more than overseas-imported), and vendor investment in third-party testing.

Current Market Pricing (2026)

The pattern is clear: 30mg is the sweet spot — it drops per-mg cost by ~30% versus 10mg while staying within the 28-day stability window at almost any dose. Jumping to 60mg saves another 10-20% per mg but requires confident commitment to a sustained protocol. Our Peptide Price Index Q1 2026 put tirzepatide as the most-tracked peptide in the dataset (218 observations, 7 vendors, median $5.50/mg) with the lowest stockout rate of any deep-dive peptide at 3.2%.

Cost Per Week at Common Doses

For current vendor-specific pricing with exact $/mg breakdowns, see our Best Tirzepatide Vendors comparison.

How to Verify Tirzepatide Quality

Tirzepatide is not a simple peptide. It’s a 39-amino-acid dual agonist with two non-coded aminoisobutyric acid (Aib) residues, an amidated C-terminus, and a C20 fatty-diacid side chain connected via a PEG linker to the lysine at position 20. Synthesis is expensive and error-prone. If a vendor isn’t showing you a recent COA, you have no idea what’s in the vial.

What a COA (Certificate of Analysis) Should Include

Identity Confirmation

• Mass spectrometry confirming the correct molecular weight (4,813.52 Da for tirzepatide)
• Amino acid sequence verification with the Aib modifications at positions 2 and 13
• Confirmation of the C20 fatty acid conjugation

Purity Testing

• HPLC purity — look for 98%+ purity
• The chromatogram should show a single dominant peak with minimal truncated-sequence impurities

Contamination Testing

• Endotoxin levels (bacterial contamination)
• Residual solvent analysis (acetonitrile, TFA)
• Heavy metals screening

How to Verify a COA Is Legitimate

1. Check the testing lab — Reputable labs include Janoshik Analytical, MZ Biolabs, and Colmaric Analyticals. Avoid vendors who only show “in-house” testing.
2. Verify on the lab’s website — Janoshik COAs have a task number you can look up directly at janoshik.com. If the vendor won’t provide a verifiable task number, that’s a red flag.
3. Check the date — COAs should be recent (within 6 months). Old COAs may not represent the current batch.
4. Match the batch — The batch/lot number on the COA should match what’s printed on your vial.
5. Look for the original PDF — Screenshots are easier to fake than full PDFs with lab letterhead and signatures.

Red Flags to Avoid

• No COA available — for a peptide this complex, zero testing is a hard pass
• Only in-house testing — self-reported purity numbers are meaningless
• Prices below $2/mg across all sizes — synthesis costs make this implausible without corner-cutting
• No contact information — legitimate vendors have real customer service
• Cryptocurrency only — good vendors accept crypto but also standard payment rails
• No return or reship policy — reputable vendors stand behind their products