How long do peptides take to work? The honest range is hours to months, depending on the molecule and what is being measured. Appetite may feel different in the first days after a GLP-1 injection, but controlled tirzepatide evidence measures appetite and energy intake at week 3; body-weight results accumulate over months. Growth-hormone secretagogues can change GH and IGF-1 laboratory values within days to weeks, while body-composition trials use months. For BPC-157, animal studies run days to weeks, but no human trial establishes a results timeline. NAD+ infusion research tracks metabolites over hours and does not establish durable clinical effects.
There is no single peptide results timeline because “working” could mean a quieter appetite, a change in a blood marker, a trend on a scale or better function. Those endpoints move on different clocks.
How long do peptides take to work by outcome?
| Category | Earliest defensible checkpoint | What is measured | Main limit |
|---|---|---|---|
| GLP-1 medicines such as tirzepatide | Appetite may be noticed in days; controlled evidence at week 3 | Appetite, energy intake, then weight trend | Early appetite does not predict an individual's final weight |
| GH secretagogues | Days to weeks for GH or IGF-1; months for body composition | Blood tests first, body composition later | Data for one secretagogue do not establish a timeline for every blend |
| BPC-157 and other healing peptides | Days to weeks in animal experiments | Tissue, function and biomechanical endpoints | No human trial defines when BPC-157 starts working |
| NAD+ | Two to six hours for measured metabolites during an infusion | Plasma and urine metabolites | Acute metabolism is not evidence of a lasting clinical outcome |
These are evidence landmarks, not promises. The clock also changes with the condition, baseline health, treatment route and the endpoint chosen before treatment begins. A lab value can move before anything feels different. A subjective change can also happen without an objective outcome following it.
The first signal is not the final result
A useful timeline has at least three points: biological activity, an early measurable response and a meaningful clinical outcome. They should not be collapsed into one date.
Tirzepatide can affect appetite before the scale shows a stable trend. A GH secretagogue can alter IGF-1 before a body-composition scan would be informative. An infusion can change a metabolite during the appointment without showing what happens weeks later. This is why “I felt something on day one” and “the treatment changed the outcome we chose” are different statements.
The comparison should also stay within the same compound. Tirzepatide, CJC-1295, ipamorelin and BPC-157 act through different pathways. A fast signal from one does not make another slow, and a slow endpoint does not mean nothing is happening.
GH secretagogues: labs first, body composition later
Human CJC-1295 research gives a clear example of the lab clock. In two small randomized ascending-dose studies lasting 28 and 49 days, a single CJC-1295 injection was associated with mean GH levels two to ten times baseline for at least six days and mean IGF-1 levels 1.5 to three times baseline for nine to 11 days. After repeated doses, mean IGF-1 remained above baseline for up to 28 days (Teichman et al., Journal of Clinical Endocrinology & Metabolism, 2006).
That study measured hormones. It did not establish when someone using CJC-1295 with ipamorelin would see a body-composition result. A broader secretagogue trial in 395 older adults studied capromorelin, not CJC-1295 or ipamorelin. At six months, lean body mass had increased by 1.4 kg in the pooled treatment groups and 0.3 kg with placebo (White et al., Journal of Clinical Endocrinology & Metabolism, 2009). That class reference explains why body-composition follow-up is measured in months, but it is not a forecast for another molecule. The evidence review on whether sermorelin works applies the same distinction between hormone changes and outcomes.
Healing peptides and NAD+ have narrower evidence
BPC-157 has no human randomized trial that supplies a “starts working” date. One frequently cited study involved rats with transected Achilles tendons, plus cultured tendon cells. Researchers assessed the rats on days 1, 4, 7, 10 and 14 and reported differences in functional, microscopic and biomechanical measures (Staresinic et al., Journal of Orthopaedic Research, 2003). Those timepoints describe an animal experiment, not a two-week human expectation. The BPC-157 evidence overview separates those preclinical findings from what has actually been studied in people.
NAD+ is not a peptide, although it is often grouped with peptide therapy. Its timeline is sometimes described as immediate because an infusion happens in a single visit. The human evidence is much narrower. A small 2019 pilot tracked NAD+ and its metabolites during a six-hour intravenous infusion. Plasma values did not change for the first two hours, while urinary NAD+ and methyl-nicotinamide were higher at six hours (Grant et al., Frontiers in Aging Neuroscience, 2019). The study described acute metabolic handling; it did not test lasting energy, cognition or longevity outcomes. The NAD+ injection overview covers what the route means without turning an infusion-day observation into a long-term claim.
GLP-1s: appetite first, weight over months
Some people notice appetite changes within days of a GLP-1 dose, but the controlled checkpoint is later. In a 2025 randomized phase 1 trial of 114 adults, tirzepatide reduced energy intake at week 3 by an estimated 524.6 calories at an unrestricted lunch versus placebo. Participants also reported lower overall appetite, hunger and food cravings (Martin et al., Nature Medicine, 2025).
Weight is a slower outcome. SURMOUNT-1 followed 2,539 adults for 72 weeks, including 20 weeks of dose escalation. Mean weight change at week 72 was −15.0%, −19.5% and −20.9% across the three tirzepatide groups, compared with −3.1% for placebo (Jastreboff et al., New England Journal of Medicine, 2022). The full tirzepatide weight-loss results page puts that curve in context. A week of reduced appetite cannot be converted into a personal 72-week result.
How a prescriber decides whether the clock is meaningful
The follow-up plan should name the outcome before it names the deadline. For a GLP-1, that might include appetite, tolerability and a multiweek weight trend. For a GH secretagogue, it may include IGF-1 and later body-composition measures. For a recovery goal, function matters more than a vague sense that tissue is changing.
Prescribers also look for reasons a response may be hard to interpret: inconsistent use, another medication, a changing exercise load or an endpoint measured too soon. They may continue, adjust or stop a protocol based on the whole picture. At Promise, a licensed provider reviews every request, and not everyone qualifies. Whether a compounded formulation belongs in a care plan is a decision between the patient and the licensed provider.