KLOW Peptide Blend side effects

What is known about the blend itself

No study has measured side effects of KLOW, in animals or in people.¹ The closest records are two complaint reports about "blended TB-500 and BPC-157", two of its four parts, which FDA found during its 2026 review; the reports did not include safety assessments.³ Trade press reported that at FDA's July 2026 advisory meeting, one committee member raised concern that TB-500 is being used in combination with other peptides.⁵

FDA's adverse event database held no reports for TB-500 through March 26, 2025,³ and none for KPV through December 3, 2025.⁴ FDA notes that reporting to this database is voluntary, so the absence of reports does not show that no harm occurred.⁴

Reported in people

Mild or no events in small studies

• BPC-157 enemas. Headache and flatulence were the adverse events reported most often in healthy volunteers given BPC-157 as an enema; the meeting abstracts give no rates.²
• Other small BPC-157 studies. No serious adverse events appear to have been reported, but FDA notes these studies were short and small and gave limited safety information.² The 12-woman bladder study reported no adverse events,⁶ and a 2-person IV pilot reported no adverse effects.⁷
• Thymosin beta-4, not TB-500. In a placebo-controlled trial of IV full-length thymosin beta-4 in 40 healthy volunteers, adverse events were infrequent and mild or moderate.⁸

Single reports to FDA, cause not established

FDA's review lists these reports from its adverse event database and says it is unclear whether BPC-157 caused them.²

• Injection site. A woman using BPC-157 injections had 9 days of redness and swelling around the injection site, but she was also injecting compounded thymosin.⁹
• Breathing. A 28-year-old man developed shortness of breath, which led to an emergency room visit, after injecting BPC-157 acetate under the skin.¹⁰
• Skin and gums. A 40-year-old woman injecting a research-labeled product with BPC-157 and TB-500 under the skin twice daily developed diffuse skin darkening and darker gums, and the same reaction returned when she used it again two weeks later.² It involved two of KLOW's four parts.

Seen in animal studies

• Clotting and liver. In 28-day studies with daily injections into muscle, BPC-157 was linked to signals FDA judged clinically relevant: altered clotting tests (aPTT shorter in rats, longer in dogs) and liver-related changes (higher ALT, glucose and triglycerides).²
• Other toxicity. A 2020 preclinical safety study found mild irritation in a local tolerance test and lower creatinine in dogs at 2 mg/kg, but not at lower doses.¹³ Otherwise BPC-157 was well tolerated in its tests in mice, rats, rabbits and dogs, with no genetic or embryo-fetal toxicity.¹³
• Pregnancy. In rats, BPC-157 injected into muscle at up to 4 mg/kg/day on gestation days 6 to 15 caused no fetal malformations.¹¹ FDA found no study covering a complete reproductive cycle.¹¹
• Gaps. FDA found no carcinogenicity studies of BPC-157 or TB-500, and no developmental or reproductive studies of TB-500.²³ For KPV, FDA found no animal toxicity studies of any kind.⁴

Risks FDA and reviewers describe

These risks are named in reviews and warnings. How often they occur is unknown.

• Immune reactions. FDA says injected BPC-157, TB-500 and GHK-Cu may provoke immune reactions, a risk raised by peptide clumping (aggregation) and impurities.²³¹⁴ FDA adds that, in general, injection under the skin is linked to more immune reactions than injection into a muscle or vein.³
• Copper. A 2026 review calls copper a recognized contact sensitizer in susceptible people¹⁵ and says repeated injection of GHK-Cu should be evaluated for copper build-up in the liver and, at high exposures, the nervous system.¹⁶ In large amounts, copper is poisonous.¹⁷ KLOW does not disclose how much GHK-Cu it holds.
• Product quality. FDA found BPC-157, TB-500 and KPV sold as multiple salts and derivatives under the same common names, and certificates of analysis that lacked tests for impurities, bacterial endotoxins or aggregates.²³⁴
• Unregulated supply. A 2026 review warns that unapproved peptides such as BPC-157 and TB-500 lack established human safety profiles and carry risks including contamination, manufacturing impurities, inaccurate dosing, abnormal blood vessel growth and cancer development.¹⁸ FDA says injectable products can pose risks of serious harm because they bypass some of the body's key defenses against toxins and microorganisms.¹⁹
• Class warnings. Health Canada lists risks of unauthorized injectable peptide drugs, including liver or kidney damage, blood clots and the growth of cancerous tumors.²⁰ Its April 2026 advisory names all four of KLOW's peptides among examples of products it has seized.²⁰ These warnings cover the group, not effects measured for KLOW's parts.

Warnings

• No safe dose is known. USADA says it is unknown whether any dose of BPC-157 is safe,²¹ and FDA calls the human safety risks of TB-500 and KPV unknown.³⁴
• Long-term use. FDA found no repeat-dose toxicity study of BPC-157 longer than 28 days.¹²
• Pregnancy. Animal reproductive testing is incomplete for BPC-157 and absent for TB-500 and KPV,²³⁴ and FDA found no human exposure data at all for TB-500 or KPV.³⁴
• Athletes. BPC-157 is prohibited under WADA class S0 and TB-500 under S2,²²²³ and from January 1, 2027 the list names peptides in general under S0.²³

Related pages

Back to the full profile: What is KLOW Peptide Blend?. Study findings are in KLOW Peptide Blend benefits and uses, and amounts used in research in KLOW Peptide Blend dosage. Single-peptide safety pages: TB-500 side effects and KPV side effects. The three-peptide blend is covered in Glow Peptide Stack side effects, and general precautions in Peptide safety basics. Vial specifications and storage are on the KLOW Peptide Blend for sale page.