If you are tired most days, a peptide sold for “energy” can sound like a direct fix. The research is thinner than the marketing.
None of the studies below measured energy by that name. Each measured something narrower, like a fatigue score or muscle strength. This page names that measure every time, so you can see what was tested.
NAD+: levels go up, fatigue scores do not
NAD+ is the peptide-adjacent compound most often sold for energy. It is a coenzyme that cells need for energy metabolism. The question is whether taking more changes how you feel.
A 2025 trial tested nicotinamide riboside, a pill that the body turns into NAD+ [3]. It enrolled 58 adults with long COVID. One group took 2,000 mg a day for 20 weeks. The other took placebo for 10 weeks, then the supplement.
Blood NAD+ rose 2.6- to 3.1-fold within 5 to 10 weeks. But fatigue scores did not differ from placebo (p = 0.59). Nor did sleep, mood or thinking.
Within-group gains appeared after 10 weeks, but only in an exploratory analysis. Dropout was high: 51.4% of the group on the supplement throughout had left by week 20.
That trial used an oral precursor, not NAD+ injections. The injection evidence is reviewed in NAD injection benefits.
Weight-loss peptides: better function, some fatigue
Semaglutide is a peptide too, and its main trial asked people how well they could move through daily life.
In STEP 1, 1,961 adults with overweight or obesity took semaglutide or placebo for 68 weeks [1]. The semaglutide group reported a greater increase in physical functioning.
The label shows the other side. Fatigue was reported by 11% on the 2.4 mg dose and 5% on placebo [2]. So the same drug can leave some people more able and others more tired.
That trade-off is worth naming before you start. The full list is in semaglutide side effects.
Sermorelin and growth hormone signals
Sermorelin is a short form of growth-hormone-releasing hormone. It is marketed for energy on the idea that more growth hormone means more vigor.
A 1997 study gave 11 healthy men aged 64 to 76 nightly injections of GHRH 1-29, the same peptide, at 2 mg for 6 weeks [4]. Night-time growth hormone rose (P < .02).
Two of six strength measures improved, as did one endurance test. Body composition, IGF-1 and blood sugar did not change. The abstract describes 11 treated men and no placebo group, so practice or chance cannot be ruled out.
The authors suggested a single nightly dose was less effective than several daily doses. Sermorelin is covered more fully in the sermorelin guide.
MOTS-c: a mouse result
MOTS-c is a small peptide made from instructions in mitochondria, the parts of cells that produce energy. That origin is why it is marketed for stamina.
A 2021 study found it improved physical performance in young, middle-aged and old mice [5]. Late-life treatment, started at 23.5 months, also raised physical capacity in mice.
In people, the same study found only that exercise raises the body’s own MOTS-c. Nobody was given MOTS-c. The wider record is in MOTS-c evidence.
| Compound | What was measured | In whom | Result |
|---|---|---|---|
| NAD+ precursor (oral) | Fatigue severity scale | 58 adults with long COVID | No difference from placebo |
| Semaglutide | Physical functioning (self-report) | 1,961 adults with obesity | Greater improvement than placebo |
| Semaglutide | Fatigue as a side effect | Weight-trial participants | 11% vs 5% on placebo |
| GHRH 1-29 (sermorelin) | Strength and endurance | 11 older men, no placebo group described | 2 of 6 strength tests improved |
| MOTS-c | Physical performance and capacity | Mice | Improved; not tested in people |
Where to start if you are tired
Fatigue has many causes, including thyroid, iron, sleep and mood. A prescriber can test for the common ones before you add anything.
If you still want to try a peptide, ask which endpoint its evidence measured. For NAD+, compare formats in the NAD+ injection or nasal spray rankings. Its skin claims are reviewed separately in NAD+ benefits for skin.
More options with human studies are gathered on the longevity goal page.