Can I Take Glycine With Adderall XR?
Glycine, the amino acid supplement often taken at bedtime for sleep, has no known pharmacokinetic interaction with Adderall XR (mixed amphetamine salts, extended-release, Schedule II, FDA-approved for ADHD in patients age 6 and older). The two substances are absorbed and cleared through different pathways, so glycine should not raise or lower amphetamine blood levels, and amphetamine should not change how glycine is absorbed. The open question is not whether the combination is dangerous but whether the timing matters for sleep, and whether people with a personal or family history of psychosis or bipolar disorder should treat the combination differently. Nothing here is dosing advice for an individual reader; verify any specific regimen with the prescriber managing the Adderall XR, and see this breakdown of Adderall XR food and supplement interactions for how label facts compare with internet rules.
The core answer, stated plainly
Glycine (a non-essential amino acid, typically dosed at 3 grams before bed for sleep) and Adderall XR (mixed amphetamine salts) do not share a metabolic pathway: glycine is handled by amino acid transport and does not involve the cytochrome P450 system, while amphetamine is metabolized largely through CYP2D6. No pharmacokinetic drug interaction between them has been documented. The remaining concern is pharmacodynamic and mostly theoretical: glycine is a co-agonist at the NMDA receptor and has mild sedative and temperature-lowering effects, so in someone unusually sensitive to dopaminergic or glutamatergic shifts, stacking the two agents at the wrong time of day could blur cause and effect for sleep or mood symptoms. Separating the doses by several hours resolves nearly all of this concern in practice, though no trial has tested the two substances together.
What glycine and Adderall XR each are
Glycine is the simplest amino acid in the body. It functions as an inhibitory neurotransmitter in the spinal cord and brainstem and as an obligatory co-agonist at NMDA-type glutamate receptors in the cortex. It has Generally Recognized As Safe (GRAS) status from the FDA as a food ingredient; supplement doses used for sleep are typically in the 3-to-5 gram range, well below the doses studied for other purposes.
Adderall XR is the extended-release brand of mixed amphetamine salts, combining dextroamphetamine and levoamphetamine in a fixed ratio. It is FDA-approved for ADHD and, in a separate formulation, for narcolepsy. It works by reversing dopamine and norepinephrine transporters, increasing synaptic concentrations of both neurotransmitters. The extended-release capsule is designed to release drug in two phases, giving a longer duration of action than immediate-release amphetamine, which is the reason once-daily morning dosing is standard practice according to the FDA label (Adderall XR prescribing information).
Why people combine them
Two reasons come up most often. First, stimulant medications can delay sleep onset and shorten total sleep time even when taken early in the day, and patients look for a non-sedating-prescription way to counteract that. Glycine has been studied in small human trials as a sleep aid, with some evidence that a bedtime dose modestly shortens the time it takes to fall asleep and reduces next-day fatigue in healthy adults. Second, glycine is a component of collagen and glutathione synthesis, and some people supplement it for general metabolic reasons unconnected to their stimulant prescription.
Both rationales are reasonable starting points for a conversation with a prescriber. Neither has been tested specifically in people taking Adderall XR, which is the central evidence gap this page cannot close.
Is there a pharmacokinetic interaction?
No published study has tested glycine and amphetamine given together in humans, and no plausible metabolic overlap has been identified. Glycine is absorbed through intestinal amino acid transporters and is not a substrate, inhibitor, or inducer of the cytochrome P450 enzymes that metabolize amphetamine. Protein binding is low for both compounds. Based on these separate pathways, a clinically meaningful pharmacokinetic interaction is not expected, but "not expected" is not the same as "proven absent" in the absence of a direct trial.
One theoretical mechanism is sometimes raised: amphetamine renal clearance is sensitive to urine pH, with acidic urine speeding excretion. Glycine metabolism can generate ammonium ions, which in principle could acidify urine slightly. Whether a standard 3-to-5 gram glycine dose produces a large enough pH shift to meaningfully change amphetamine clearance has not been studied and should be treated as unconfirmed. Patients already avoid large doses of urinary alkalinizers (high-dose sodium bicarbonate, very high-dose vitamin C) close to their Adderall XR dose per standard stimulant prescribing guidance; that caution is unrelated to glycine specifically.
Is there a pharmacodynamic interaction?
This is the more genuine question. Glycine is a co-agonist at the NMDA receptor's glycine-B site, and NMDA receptor signaling in the prefrontal cortex intersects with the same circuitry that amphetamine's dopamine-releasing action affects. Much higher doses of glycine (many times the sleep dose, in the tens of grams daily) have been studied as an add-on treatment for negative symptoms of schizophrenia, reflecting an attempt to boost NMDA function pharmacologically. Ordinary sleep-support doses of 3 to 5 grams are far below that range, and there is no direct evidence that they meaningfully shift NMDA receptor activity in a way that would interact with amphetamine's effects.
That said, the mechanism is not zero. In a person with an underlying vulnerability to psychosis or mania, a stimulant already carries a recognized risk of triggering or worsening symptoms. Adding an NMDA-active supplement, even at a low dose, is not something that has been tested in that population, and caution rather than confidence is the honest position.
Sleep: the most common reason this question comes up
Stimulant medications, including Adderall XR, are commonly associated with insomnia and delayed sleep onset as a class effect, and this is described as a common adverse effect in the FDA label and in ADHD treatment literature generally. Small human trials of bedtime glycine have reported modest improvements in subjective sleep quality and next-day alertness, generally at doses around 3 grams. These trials were not conducted in people taking stimulant medication, so the effect size in that specific population is unknown. A reasonable, low-risk framing is that glycine is one of several non-pharmacological options worth trying for stimulant-associated insomnia before escalating to a prescription sleep aid, alongside sleep hygiene measures and adjusting the timing of the stimulant dose itself.
Because Adderall XR has a long duration of action, taking the stimulant as early in the day as the treatment plan allows, and taking glycine several hours later at bedtime, keeps the two effects from overlapping in time. This is a timing principle based on pharmacology, not a tested clinical protocol.
Evidence-status interaction assessment
| Status | Claim | Basis |
|---|---|---|
| Established | Glycine and amphetamine are metabolized through different, non-overlapping pathways (amino acid transport vs. CYP2D6/beta-hydroxylation). | Basic pharmacology of each compound; FDA label for Adderall XR metabolism. |
| Established | Stimulant medications including Adderall XR are commonly associated with insomnia and delayed sleep onset. | FDA label; well-documented class effect in ADHD pharmacotherapy. |
| Plausible, not proven in this combination | A 3-to-5 g bedtime glycine dose may modestly improve sleep onset and reduce next-day fatigue in people taking Adderall XR. | Small human sleep trials of glycine alone, not conducted in stimulant users; extrapolation required. |
| Plausible, not proven | Glycine's NMDA co-agonism could theoretically interact with amphetamine-driven dopamine signaling in a susceptible individual. | Receptor pharmacology; no direct clinical data connecting standard glycine doses to this outcome. |
| Not established | Glycine changes urinary pH enough to meaningfully alter amphetamine clearance or duration of effect. | No dedicated study; theoretical mechanism only. |
| Not established | Long-term (beyond a few weeks) safety or efficacy of glycine specifically in stimulant-treated patients. | No trials of this duration in this population have been identified. |
| Verify with prescriber or pharmacist | Whether glycine is appropriate given the individual's psychiatric history, kidney function, and current medication list, and what dose and timing fits their specific Adderall XR schedule. | Requires clinical judgment beyond what a general reference page can provide. |
Practical monitoring if the combination is used
| Parameter | Why it matters | What to watch |
|---|---|---|
| Sleep-onset time and quality | Primary reason people add glycine | Should stay stable or improve; worsening suggests reconsidering dose or timing |
| Daytime alertness and stimulant effect | Screens for any unexpected reduction in Adderall XR's perceived duration | Report a clear change in how long the medication seems to last |
| Mood, anxiety, or new psychotic-type symptoms | Both agents touch dopaminergic/glutamatergic signaling | Any new or worsening symptoms warrant prompt discussion with the prescriber, not self-adjustment |
| GI tolerance of glycine | Higher glycine doses can cause nausea or loose stool | Start low (around 3 g) before considering an increase |
| Kidney function, if relevant | Glycine is renally cleared after conversion to oxalate | Patients with reduced kidney function should discuss dose limits with their clinician |
Who should not combine these without explicit medical guidance
- Anyone with a personal or family history of bipolar disorder, schizophrenia, or stimulant-associated psychosis, given the theoretical NMDA/dopamine overlap described above.
- Children and adolescents: Adderall XR is FDA-approved down to age 6, but glycine supplementation in children has mainly been studied for inborn errors of metabolism, not as a sleep aid alongside stimulants. A pediatrician should approve any addition.
- Pregnant or breastfeeding patients: glycine is a normal dietary amino acid, but supplemental dosing alongside stimulant therapy in pregnancy has not been separately studied. This combination should go through the prescribing clinician rather than being started independently.
- Anyone with significantly reduced kidney function, given glycine's renal clearance pathway.
When to seek urgent care rather than adjusting supplements at home
New chest pain, a racing or irregular heartbeat, severe agitation, hallucinations, or any signs of an allergic reaction after starting a new supplement warrant urgent medical evaluation rather than waiting to discuss at a routine appointment. These symptoms are not expected effects of glycine and should not be assumed to be caused by it without evaluation.
What this page cannot tell you
No randomized trial has tested glycine given alongside Adderall XR or any amphetamine product, in any population. Everything above is built from the separate pharmacology of each substance, small trials of glycine alone for sleep, and general FDA labeling information for Adderall XR. Specific numbers sometimes circulated for this topic, such as exact percentages of patients affected by stimulant insomnia or precise minute-by-minute changes in sleep latency from glycine trials, could not be independently verified against a confirmed primary source for this draft and should be checked against the original literature before being published with confidence. Where a precise figure could not be confirmed, this draft has stated the finding qualitatively instead of presenting an unverified number as fact.
Bottom line
Glycine and Adderall XR do not appear to conflict at the level of drug metabolism, and separating the doses by several hours addresses most of the plausible pharmacodynamic overlap. The supplement is not FDA-approved as a treatment for stimulant-related insomnia, and its use for that purpose is an off-label, evidence-informed choice rather than a guideline-backed one. Confirm any specific plan, especially dose, timing, and duration, with the prescriber managing the Adderall XR, and flag any psychiatric history before starting.
References
- U.S. Food and Drug Administration. Adderall XR (mixed amphetamine salts extended-release) prescribing information. https://www.accessdata.fda.gov/drugsatfda_docs/label/2013/021303s026lbl.pdf
Reported figures on sleep-related glycine trials and stimulant-associated insomnia prevalence vary between studies and have not been independently confirmed here, so they should be interpreted with caution.