Retatrutide and GHK-Cu, Plus the GLOW and KLOW Blends

No trial has tested retatrutide and GHK-Cu together, and we found no published human trial of GHK-Cu as an injection at all. Its human data come from a few small studies of creams and serums on the skin. "Reta and GLOW" or "reta and KLOW" means two separate vials: retatrutide for weight, plus a ready-mixed blend built around GHK-Cu that people hope will look after skin, hair and gut as the weight comes off. KLOW doesn't contain retatrutide.

Much of what you'll read about these blends comes from people selling the vials. This page sticks to what has been measured in people.

What reta, GLOW and KLOW actually contain

GHK-Cu is a small peptide that carries copper. It's three amino acids long (glycine, histidine and lysine), and your body makes it on its own. A 2018 review in the International Journal of Molecular Sciences puts blood levels of GHK at about 200 ng/mL at age 20 and 80 ng/mL by age 60, and notes GHK-Cu is common in skin and hair products.

GLOW and KLOW are seller names for pre-mixed vials, with no official recipe. On the listings we saw on September 29, 2026, the usual versions looked like this:

Nothing stops a seller from changing the recipe, so read the vial, not the nickname. BPC-157 is a synthetic 15-amino-acid peptide that a 2026 trial record describes as derived from human gastric juice. TB-500 is a fragment of thymosin beta-4, a natural protein. KPV is three amino acids long.

None of these blends contains retatrutide; some sellers just bundle a retatrutide vial with a GLOW or KLOW vial. People who add MOTS-c are building a different stack, covered on our page on retatrutide and MOTS-c.

Retatrutide and GHK-Cu in people, ingredient by ingredient

Retatrutide has far more human data than the other four combined, and the combination has none. We checked all 33 retatrutide studies on ClinicalTrials.gov on October 31, 2026, and none adds GHK-Cu, BPC-157, TB-500 or KPV.

The FDA wording comes from its page on compounding substances that may carry significant safety risks, current as of April 22, 2026. It also flags a possible risk of immune reactions (immunogenicity) for GHK-Cu, BPC-157 and TB-500, tied to impurities and, for GHK-Cu and TB-500, clumping.

A review in Pharmaceutics in August 2026 set out to list every human GHK-Cu study. The list is short: a small topical study from 1998, a cosmetic report from a 2002 conference, a randomized study after CO2 laser skin treatment in which 13 people finished follow-up and GHK-Cu showed no objective advantage, and a 2026 study of a 2% eyebrow serum in 18 healthy people that reported more and thicker brow hairs. The authors add that no validated safe-exposure threshold for GHK-Cu has been set in people.

Every GHK-Cu trial we found on ClinicalTrials.gov on October 31, 2026 uses the peptide on the skin or measures it in blood. One tests a 0.1% gel on small skin wounds (60 people planned, Shenzhen, primary completion February 2027). A LifeWave patch study, not yet recruiting, will measure GHK-Cu in the blood of 100 healthy adults, and an aging study uses it as one ingredient in a skin serum. None injects it. The gel's sponsor, Hudson Biotech, also filed one of the two BPC-157 injection trials and the TB-500 entry that calls itself fictional, so we'd wait for published results before counting any of them.

Why people add GHK-Cu to retatrutide

The logic: retatrutide takes weight off fast, fast loss can leave loose skin and thinner hair, and GHK-Cu is famous in skin care. The first part is solid: in TRIUMPH-1, people on 12 mg lost 28.3% of their body weight on average over 80 weeks by Lilly's efficacy estimand (as if everyone stayed on the drug), and 62.5% of them lost a quarter or more. Counting everyone randomized, the NEJM average was 25.0%.

The rest has gaps. None of Lilly's trial releases, Phase 3 abstracts or Phase 2 registry tables that we checked report hair loss, so retatrutide's rate is unknown. Tirzepatide gives the nearest clue: on the Zepbound label, 4% to 5% of people on the drug had hair loss against 1% on placebo, and among women it was 7.1%. That's tirzepatide data, not retatrutide. Our retatrutide and hair loss guide explains why shedding happens.

For GHK-Cu and hair, the closest evidence is that 18-person eyebrow serum study. Nobody has tested whether GHK-Cu, by any route, changes loose skin, a thinner face or hair shedding after big weight loss. Our muscle loss page covers the other loss people worry about, and retatrutide before and after covers the loose-skin question.

Our read: the only human data for GHK-Cu come from products put on the skin, so the injected blend is the least-studied way to use it. A cream at least has small human studies behind it, even if one of them found no objective benefit.

Where the risks pile up

Start with what retatrutide does on its own. About 4 in 10 people on 12 mg (42.4%) had nausea in TRIUMPH-1, against 14.8% on placebo. In TRANSCEND-T2D-2, a type 2 diabetes trial reported October 28, 2026, 12 mg had diarrhea in 32.7% of people against 26.4% on Ozempic 2 mg, and 7.9% stopped because of side effects against 2.7%.

Some people count on the BPC-157 and KPV in KLOW to protect the gut from exactly those symptoms. FDA has found no human exposure data for KPV by any route, and the BPC-157 injection trials we found date from 2026, with no results yet. Nobody has measured whether either eases nausea or diarrhea on retatrutide.

The copper in a GLOW or KLOW vial

PubChem's molecular weights let you work out how much copper GHK-Cu carries. A label that just says "GHK-Cu" doesn't tell you which form is inside, and the two forms differ almost twofold.

The NIH Office of Dietary Supplements puts adults' recommended intake at 900 mcg a day, with an upper limit of 10,000 mcg (10 mg) a day from food and supplements. A 50 mg vial holds about 5 to 9 times the daily recommended amount, though a vial lasts several injections; per milligram of GHK-Cu, the copper is 86 to 158 mcg. Those intake figures are for copper you swallow. The 2026 Pharmaceutics review says they can't be converted into limits for injected copper, and no such limit has been set.

One more unverified product per vial

Retatrutide bought online comes with no guarantee of what's inside. In June 2026, Victoria's Chief Health Officer reported 6 cases of acute liver injury since January in people who used products labelled Retatrutide, possibly caused by a contaminant. In a September 2026 alert, Australia's TGA reported that a vial sold as retatrutide held no retatrutide, only undeclared semaglutide at about 8 times the level in approved products.

Health Canada's April 9, 2026 advisory lists examples of unauthorized injectable peptides it has seized, and all five ingredients of reta plus KLOW are on it: retatrutide, GHK-Cu, BPC-157, TB-500 and KPV. It warns that such products can hold too much, too little or none of the active ingredient, plus contaminants such as heavy metals, particles or bacterial toxins (endotoxins).

Can reta and KLOW be taken together?

Nobody knows, because nobody has tried it under study conditions. There's no interaction data, no data on mixing the two in one syringe, and no data on whether a copper complex stays stable next to retatrutide.

The label numbers show how a fixed blend behaves. Every milligram of KLOW is 0.625 mg of GHK-Cu and 0.125 mg each of the other three (GLOW is about 0.71 mg of GHK-Cu per milligram). You can't change one ingredient without changing all of them, so a blend can't be adjusted around a side effect the way a single peptide can. TRIUMPH-1 used retatrutide alone, starting at 2 mg once a week and stepping up every 4 weeks; the retatrutide dosage page lists each schedule.

Retatrutide alone already produces large losses, so no one can credit a weight, skin or hair change on this stack to the blend. In the Phase 2 trial, the 12 mg group averaged 17.5% at 24 weeks (NEJM) and 24.2% at 48 weeks (Lilly, efficacy estimand). Forum posts about reta and KLOW are user reports with no comparison group on retatrutide alone, and we haven't quoted any.

Our read: until someone runs that comparison, a good result on the stack tells you retatrutide worked, not that KLOW did.

Buying two vials means checking two batches

Neither half of this stack has an official price. Retatrutide has no approved version, so anything sold online isn't Lilly's product, and GLOW and KLOW aren't approved drugs in the US or Canada. We haven't quoted online prices, because a price says nothing about what's in the vial. Our page on retatrutide for sale explains what's actually being sold, and with a stack the checks double:

• a batch-specific test report for each vial, with a batch number that matches the label
• identity and amount for every peptide in a blend, not one purity figure for the whole vial
• the copper content, and which form of GHK-Cu, for anything that contains it
• endotoxin or sterility results, since every vial here is injected

Routes with real data behind them

Lilly's October 2026 FAQ says retatrutide "has not been reviewed or approved by the FDA or any regulatory agency in the world, and no one can legally sell it for human use." Outside a trial there is no legal retatrutide, and our how to get retatrutide and is retatrutide legal pages cover the routes. Lilly's expanded access program is for adults with a BMI of 35 or more despite the highest available dose of a weight-management drug, with 2 or more serious obesity-related complications, who can't join a trial. A doctor makes the request.

Lilly last said, on September 29, 2026, that it plans to submit retatrutide to the FDA in the first quarter of 2027 as a Biologics License Application (BLA). On October 2, 2026, the FDA decided that retatrutide is a drug, not a biological product, so an application would need to be filed under section 505 of the Federal Food, Drug, and Cosmetic Act. Lilly's appeal on that question is pending in the Seventh Circuit, and we found no ruling as of October 31, 2026.

For hair, ask your doctor to look for other causes of shedding first. Other pairings have their own pages: retatrutide and tesamorelin, cagrilintide and tirzepatide, plus the overview at retatrutide stack.

If you already take reta with GLOW or KLOW, write down each vial's name, batch number and amount, and bring that list to every appointment.