Timing a GH secretagogue: bedtime or before a workout?
The body's own GH rhythm, when the studies dosed, and the head-to-head that does not exist.
Checked 2026-10-22 Researched and written by Kymata Health Editorial · Sources cited inline Report an error
Short answer
No human study has compared a GH secretagogue taken before exercise with one taken before bed, on GH, IGF-1 or anything else. What is known: the largest natural GH pulse comes with the first deep sleep, and exercise raises GH for about an hour. Trials of tesamorelin dosed in the morning in one study and at bedtime in another.
When does the body release growth hormone?
In pulses. Awake and fed, men have about 14 GH bursts a day, separated by quiet spells of roughly 2 to 2.5 hours; GH itself clears with a half-life of about 20 minutes (Hartman 1992, JCEM).
The biggest pulse comes with the first deep (slow-wave) sleep, within minutes of its onset, and moves later if sleep is delayed (Takahashi 1968, J Clin Invest; Holl 1991, JCEM). In men, about 70% of the day's GH is released in early sleep (Van Cauter 1998, Sleep).
How does exercise change GH?
Exercise raises GH in proportion to its intensity, with no threshold to cross (Wideman 2002, Sports Med; Pritzlaff 1999, J Appl Physiol). After a 30-minute bout, GH peaked 37 to 54 minutes after the start, earlier at higher intensity (Weltman 2000, J Appl Physiol).
When did the studies give GHRH analogs?
The Egrifta labels name no time of day. One tesamorelin study dosed in the morning and found larger overnight GH pulses with no change in their number (Stanley 2011, JCEM); a 20-week cognition trial dosed 30 minutes before bedtime (Baker 2012, Arch Neurol).
With GHRH(1-29), twice-daily doses raised 24-hour GH and IGF-1 in older men to the levels of young men (Corpas 1992, JCEM). Single nightly doses raised night-time GH but not IGF-1, and the authors judged them less effective than several doses a day (Vittone 1997, Metabolism). Evening GHRH also deepened slow-wave sleep in 7 men (Steiger 1992, Neuroendocrinology).
The only human study around exercise gave IV GHRH or GHRP-2 during hard cycling: GH output rose, and the two added to exercise's own effect (Maas 2000, Med Sci Sports Exerc).
So is bedtime or pre-workout better?
The evidence does not say. No study has compared the two times on any outcome, and the exercise study used IV doses during the workout, not an injection beforehand.
One factor that bears on either choice is blood fatty acids: lowering them raised the GH response to GHRP-2 and GHRH in older men (Van Dam 2000, JCEM). Timing is a decision for the prescriber.
Frequently asked questions
Questions
- Does a bedtime dose add to the natural sleep pulse?
- Not shown. GHRH at night raised night-time GH in studies, but none measured whether it adds to, replaces or reshapes the sleep-onset pulse.
- Is fasting needed?
- The tesamorelin labels do not require it. In one study, lowering blood fatty acids raised the GH response to GHRP-2 and GHRH in older men.
Not medical advice This page summarises published labels and studies. It is not a recommendation to use any product; a clinician decides.