Can I Take Glycine With Veozah (Fezolinetant)?

The Short Answer: Is Glycine Safe With Veozah?

Based on available pharmacology and published interaction databases, glycine does not appear to interfere with fezolinetant's metabolism, receptor activity, or safety profile in a clinically meaningful way. No drug interaction entry appears in the FDA label for Veozah, and no controlled study has tested the combination directly.

This is not a fully studied pairing. Glycine is an amino acid supplement increasingly popular among perimenopausal and menopausal women for sleep and metabolic support. Veozah is a prescription-only NK3 receptor antagonist approved in May 2023 for moderate-to-severe vasomotor symptoms (hot flashes and night sweats) in menopause. When two agents both target sleep architecture and neither has strong interaction data in women, clinical caution still applies.

The sections below walk through what each drug and supplement actually does, where their effects genuinely overlap, and what your life stage changes about the calculus.

How Veozah (Fezolinetant) Works

Fezolinetant is a selective, non-hormonal antagonist of the neurokinin 3 (NK3) receptor. Hot flashes in menopause occur partly because low estrogen causes the KNDy neurons in the hypothalamic arcuate nucleus to overactivate, releasing neurokinin B (NKB), which floods NK3 receptors and triggers the thermoregulatory misfiring you feel as a hot flash.

Fezolinetant blocks NK3, calming that signaling cascade.

Clinical evidence at a glance

The SKYLIGHT 1 and 2 phase-3 trials enrolled 1,022 women with moderate-to-severe vasomotor symptoms. At 12 weeks, women taking 45 mg daily experienced roughly a 60 percent reduction in daily hot-flash frequency compared with baseline, a statistically significant and clinically meaningful result versus placebo. Night sweats specifically dropped enough to measurably improve sleep in both trials.

Metabolism and the CYP1A2 pathway

Fezolinetant is metabolized primarily by CYP1A2. This is the reason strong CYP1A2 inhibitors such as fluvoxamine are contraindicated with Veozah, and why moderate inhibitors (ciprofloxacin, for example) require dose reduction. Glycine is not a CYP1A2 inhibitor or inducer. That single fact is the most important pharmacokinetic reassurance for the glycine question.

How Glycine Works

Glycine is the smallest amino acid and a conditionally essential one. At the doses used in supplements (typically 2 to 5 g), it acts primarily as an inhibitory neurotransmitter in the spinal cord and brainstem, binding glycine receptors that are separate from GABA-A or benzodiazepine receptors. It also acts as a co-agonist at NMDA glutamate receptors.

Why menopausal women reach for glycine

Sleep disruption is the most commonly reported complaint in perimenopause and early menopause, affecting up to 60 percent of women in this life stage. Glycine improves sleep onset and quality without next-day sedation, a key advantage over antihistamines or low-dose doxepin.

A randomized crossover trial by Bannai et al. gave 3 g glycine or placebo at night to adults with chronic sleep complaints. Glycine reduced sleep-onset latency, improved slow-wave sleep, and reduced daytime fatigue scores on validated scales. Participants were mostly women. The mechanism appears to involve mild hypothermic vasodilation in the skin (glycine lowers core body temperature), which is precisely the direction you want when night sweats are fragmenting your sleep.

Collagen synthesis and metabolic roles

Beyond sleep, glycine is the most abundant amino acid in collagen. Many perimenopausal women supplement it for skin, joint, and bone support. Glycine also participates in glutathione synthesis, bile acid conjugation, and heme production. None of these roles intersect mechanistically with fezolinetant's NK3 pathway.

Pharmacokinetic Interaction: Is There One?

No. Glycine is absorbed in the small intestine via sodium-coupled neutral amino acid transporters (SNAT1/2) and is not processed by hepatic cytochrome P450 enzymes at supplemental doses. Fezolinetant is absorbed orally, reaches peak plasma concentration at roughly 1.5 hours, and is cleared almost entirely by CYP1A2.

These two clearance pathways do not share enzymes, transporters, or protein-binding sites at clinically relevant concentrations. The practical consequence is that glycine will not raise or lower fezolinetant blood levels.

Pharmacodynamic Overlap: Where Effects Converge

This is the more nuanced part of the interaction picture. Both glycine and fezolinetant improve sleep in menopausal women, though through distinct mechanisms.

Sleep architecture effects

Fezolinetant reduces vasomotor-symptom-driven awakenings. Glycine facilitates sleep onset and slow-wave sleep through hypothermic and inhibitory neurotransmitter mechanisms. Together, they may produce additive sleep improvement rather than any opposing or dangerous combination. No trial has tested them together, so the additive benefit is inferred from mechanism, not measured. That is an evidence gap worth naming.

Body-temperature regulation

One intriguing area of overlap: both agents lower core body temperature during sleep, though by different routes. Fezolinetant damps the hypothalamic thermal misfiring from NK3 activation. Glycine promotes heat loss through peripheral vasodilation. Whether combining them causes excessive hypothermia is unstudied. In healthy adults at normal doses, this is very unlikely to be clinically significant, but women with cardiovascular conditions or autonomic dysfunction should mention the combination to their clinician.

Glycemic and metabolic considerations

Glycine improves insulin sensitivity in some metabolic research. A randomized controlled trial in women with metabolic syndrome found that 15 g of glycine daily for three months lowered fasting glucose and triglycerides compared to placebo. Fezolinetant has no known direct glycemic effect. This glycine-insulin pathway is relevant for women with PCOS or type 2 diabetes who are also in menopause and taking Veozah, because glycine may modestly improve metabolic markers in that context. It does not create a safety concern with fezolinetant specifically.

Life-Stage Guide: Does Your Reproductive Phase Change the Advice?

Women's bodies differ across reproductive life stages in ways that change how both glycine and fezolinetant behave. The framework below organizes the answer by stage.

Reproductive years (pre-perimenopause)

Fezolinetant is approved specifically for menopausal vasomotor symptoms and has not been studied in premenopausal women. Using it off-label in the reproductive years is not supported by current data. Glycine at dietary or low-supplement doses is appropriate across all adult life stages.

Perimenopause

This is the stage where combining glycine with Veozah is most likely to be asked, because night sweats and sleep fragmentation often begin years before the final menstrual period. Veozah is approved for women in menopause (12 months of amenorrhea), and the SKYLIGHT trials did not include perimenopausal women. If a clinician prescribes Veozah in late perimenopause, glycine at 3 g nightly is a reasonable add-on for sleep, with no pharmacokinetic concern.

Post-menopause

This is the labeled indication. Post-menopausal women often face compounding sleep problems: vasomotor disruption, circadian rhythm changes, increased pain sensitivity, and lower collagen production. Glycine addresses several of these simultaneously. The combination of Veozah and glycine in this life stage has the most rational basis and the lowest apparent risk.

Trying to conceive or recently pregnant

If you are actively trying to conceive, Veozah is not appropriate. Full details in the pregnancy section below.

Pregnancy, Lactation, and Contraception: What You Must Know

Fezolinetant is contraindicated in pregnancy. This is not a relative contraindication or a theoretical concern. The FDA label explicitly states that Veozah should not be used during pregnancy, and women of reproductive potential should use effective contraception while taking it.

Animal and human data

Embryo-fetal toxicity was observed in animal reproduction studies with fezolinetant at doses below the human therapeutic level. According to the FDA prescribing information, there are no adequate human data on fezolinetant use in pregnant women. Because NK3 signaling participates in reproductive neuroendocrine regulation, disrupting it during pregnancy carries theoretical risks that have not been fully characterized.

If you become pregnant while taking Veozah, stop the medication and contact your clinician immediately.

Contraception requirement

Because Veozah is used for menopausal symptoms, most users are post-menopausal and do not need contraception for this reason. For women in late perimenopause who still have any chance of ovulation, clinicians should confirm reproductive status before prescribing and should discuss contraception if any doubt exists.

Lactation

No human data on fezolinetant transfer into breast milk exist. The FDA label advises against use during breastfeeding. The developmental and health benefits of breastfeeding should be weighed against the mother's clinical need, but given the indication (menopausal symptoms), breastfeeding and Veozah use in combination would be a rare clinical scenario. If you are postpartum and experiencing vasomotor symptoms (which can occur with lactational amenorrhea), discuss options with your clinician before starting Veozah.

Glycine in pregnancy and lactation

Glycine at dietary levels is safe in pregnancy and is a normal component of protein-containing foods. Supplemental glycine (3 to 5 g per day) has not been studied in pregnancy-specific randomized trials. Given the absence of data, staying at or near dietary intake levels during pregnancy is the conservative approach. In lactation, glycine is present in breast milk naturally, and moderate supplemental use is unlikely to pose harm, though strong evidence is absent.

Liver Safety With Veozah: What Glycine Does (and Does Not) Change

One of the most clinically important aspects of Veozah is its liver-enzyme monitoring requirement. In the SKYLIGHT 4 open-label trial, hepatocellular injury was observed in a small number of participants, leading the FDA to require alanine aminotransferase (ALT) and aspartate aminotransferase (AST) checks at baseline and at months 3 and 6. If transaminases exceed three times the upper limit of normal, Veozah must be stopped.

Glycine is not hepatotoxic at supplemental doses. In fact, glycine has hepatoprotective properties in animal models of liver injury, and a review published in Amino Acids summarizes its anti-inflammatory role in liver tissue. There is no evidence that glycine worsens fezolinetant-related hepatotoxicity risk.

You should not add any supplement, including glycine, to your Veozah regimen without telling your prescribing clinician, because the symptom of drug-induced liver injury (fatigue, right-upper-quadrant discomfort, jaundice) can be mistaken for unrelated issues.

Conditions Where This Combination Comes Up Most Often

PCOS and premature ovarian insufficiency

Women with PCOS often experience vasomotor symptoms at a younger age, particularly after discontinuing hormonal contraception or during treatment-induced hormonal shifts. While Veozah is not approved for this context, glycine's insulin-sensitizing properties make it a reasonable supplement in PCOS independent of any Veozah use. The two do not interact metabolically.

GSM and sexual health

Genitourinary syndrome of menopause (GSM) frequently accompanies the vasomotor symptoms Veozah treats. Glycine contributes to collagen integrity in vaginal tissue in theory, though clinical trials specifically for GSM and glycine do not exist. Veozah does not treat GSM directly, so women often need additional interventions (topical estrogen, ospemifene, vaginal moisturizers) regardless of whether they are on Veozah.

Osteoporosis and bone health

Collagen is the scaffold of bone. Post-menopausal bone loss accelerates as estrogen falls, and some women supplement glycine partly for collagen support. Veozah has no known effect on bone mineral density in existing trial data. If bone health is a concern, a bone-density scan (DEXA) and discussion of bisphosphonates or other agents with your clinician should be on the agenda separately from Veozah management.

Female pattern hair loss and hormonal acne

Both conditions involve collagen and protein metabolism, and both may motivate women to use glycine supplements. Neither condition is affected by Veozah directly. Glycine at 3 to 5 g daily is a low-risk addition in these contexts.

Dosing, Timing, and Practical Guidance

Veozah is taken once daily at 45 mg, with or without food, at any consistent time of day. Glycine for sleep is typically taken at 3 g, 30 to 60 minutes before bed.

Because the two have no pharmacokinetic overlap, no dose-separation window is required. You do not need to stagger them by hours or avoid co-administration.

Practical checklist before combining glycine with Veozah:

• Confirm your baseline liver enzymes have been checked before starting Veozah.
• Disclose glycine supplementation to your prescribing clinician at your first follow-up visit.
• Start glycine at 2 g nightly and assess sleep quality over two weeks before increasing to 3 g.
• If you notice new fatigue, nausea, or yellowing of the skin while on Veozah, contact your clinician promptly. Do not attribute these symptoms to glycine without evaluation.
• Track your hot-flash frequency with a simple daily log for the first 12 weeks on Veozah, so your clinician can assess whether the drug is working at the labeled dose.

Who This Is Right For, and Who Should Wait

A good candidate for Veozah plus glycine

You are post-menopausal, confirmed by 12 months of amenorrhea. Your liver enzymes are normal at baseline. Night sweats are disrupting your sleep, and you prefer a non-hormonal approach. You have tried improving sleep hygiene and want adjunctive support. You have no contraindication to fezolinetant (no strong CYP1A2 inhibitors in your current regimen, no active liver disease).

Situations where you should discuss further before combining

You are in late perimenopause and still having occasional periods. You have a personal or family history of liver disease. You are already taking ciprofloxacin or another moderate CYP1A2 inhibitor for an acute infection. You have a history of PCOS with insulin resistance and are monitoring metabolic labs closely.

Who should not use Veozah at all

Pregnant women. Women with known hypersensitivity to fezolinetant. Women already on fluvoxamine or another strong CYP1A2 inhibitor. Women with Child-Pugh Class B or C hepatic impairment or severe renal impairment (eGFR <15 mL/min/1.73 m²).

Evidence Gap: What We Do Not Know

Women have been chronically under-represented in pharmacokinetic drug-interaction studies, and this gap is visible here. The Bannai glycine sleep trial had a small sample. The SKYLIGHT trials enrolled only menopausal women, not perimenopausal. No head-to-head or combination trial has tested Veozah plus glycine for sleep quality as a co-primary endpoint.

The statement "no interaction has been identified" is not the same as "this combination has been proven safe and effective." It means no one has looked closely enough yet to find a problem. Reporting your experience to your clinician, and asking for repeat liver function tests at your scheduled intervals, keeps you in the safest position possible while the evidence matures.

The Menopause Society's 2023 position statement on non-hormonal management of vasomotor symptoms lists fezolinetant as an effective option but does not address supplement combinations. Your clinician's individualized judgment remains the primary guide.