Two questions come up constantly around these drugs and are answered confidently far more often than the evidence permits: whether a GLP-1 interferes with oral contraception, and what it does to libido and sexual function. Both deserve a direct answer. In both cases the direct answer includes naming what has not been studied, which is the standard set out in the methodology.
Oral contraception: measured, but measured narrowly
The specific question has been tested. Forty-three postmenopausal women with type 2 diabetes took a combined oral contraceptive — ethinylestradiol 0.03 mg with levonorgestrel 0.15 mg — daily for eight days before and during semaglutide treatment at a 1.0 mg steady state, with the usual dose escalation beforehand[1].
The bioequivalence criterion was met for ethinylestradiol exposure, with a ratio of 1.11 (90% CI 1.06 to 1.15) against the prespecified 0.80 to 1.25 limits. Levonorgestrel exposure was 20% higher at semaglutide steady state, with a ratio of 1.20 (90% CI 1.15 to 1.26), and peak concentration for both was inside the bioequivalence range[1]. The conclusion the paper draws is the one in its title: semaglutide does not reduce the bioavailability of that combined oral contraceptive.
The broader interaction question has been reviewed systematically. A review of 22 reports and six prescribing sheets covering injectable GLP-1 receptor agonists given with oral medications found that treatment left peak concentration unaffected or reduced it and delayed the time to peak, across drugs of differing solubility and permeability, including contraceptive pills[2]. The review reports that these agents did not exert clinically significant changes in most of the cases examined[2]. A separate pharmacokinetic review of the approved GLP-1 agents and the dual GLP-1/GIP agonist covers the same interaction surface in more detail[3].
Two practical points follow, and neither is a reassurance. Delayed gastric emptying is the mechanism, so a drug with a narrow therapeutic index is the case to raise with a prescriber[2]. And severe vomiting, which is a common enough adverse event on these drugs to appear in every tolerability cohort, can interfere with the absorption of an oral pill for reasons that have nothing to do with a pharmacokinetic study.
Testosterone and sexual function in men: indirect, and improving
A systematic review and meta-analysis examined the effect of GLP-1 receptor agonists on testicular function in overweight and obese men. Seven studies, with 680 participants in total, entered the quantitative analysis, and treatment produced a significant increase in total serum testosterone[4]. The review’s framing is that weight loss may induce an indirect positive effect on testicular function, with recent evidence also suggesting a possible direct influence on gonadal function[4].
Erectile function specifically is less settled. A review of the question describes erectile dysfunction as a common and frequently underrecognized microvascular complication of diabetes, notes that studies of various antidiabetic therapies have produced inconsistent results, and reports that while experimental and clinical research increasingly supports a positive effect for GLP-1 receptor agonists, preliminary reports have also raised concerns in the other direction[5].
Women, libido and the gap nobody fills
The corresponding question in women is thinner still. The testosterone meta-analysis above is in men, and no equivalent body of work exists for female sexual function on these drugs. Statements about libido in women on a GLP-1 are being extrapolated from weight change, from the male hormone data, or from nothing at all. That should be said plainly rather than filled with a plausible sentence.
The honest summary across this whole cluster is short. Contraceptive drug exposure has been measured once, narrowly, and looked reassuring. Male testosterone rises, in a small meta-analysis, probably through weight loss. Erectile function is contested. Female sexual function is unstudied. Anything more definite than that is coming from somewhere other than the literature. What each seller charges is a separate matter, recorded across the seller reviews.