Can I Take Glycine with Crestor (Rosuvastatin)?

What Is Rosuvastatin and How Does It Work?

Rosuvastatin (Crestor, AstraZeneca; also available generically) is an HMG-CoA reductase inhibitor prescribed to lower LDL-C, raise HDL-C, and reduce cardiovascular event risk. It is one of the most potent statins available, capable of reducing LDL-C by 45 to 55 percent at the 20 mg dose. Unlike many other statins, rosuvastatin undergoes minimal CYP2C9 metabolism and is not a CYP3A4 substrate at all.

Pharmacokinetic Profile

The drug's absorption and distribution rely heavily on hepatic uptake transporters, specifically OATP1B1 and OATP1B3, and efflux is managed by the breast cancer resistance protein (BCRP). Any substance that blocks these transporters can raise rosuvastatin plasma concentrations substantially. The FDA-approved label notes that cyclosporine, an OATP inhibitor, raises rosuvastatin AUC by roughly 7-fold, which is why the combination carries a hard dose cap of 5 mg daily [1].

Why the Metabolic Pathway Matters for Supplement Safety

Because rosuvastatin avoids CYP3A4, the long list of supplements that interfere with that pathway, such as St. John's Wort, grapefruit-related furanocoumarins, and high-dose vitamin C in some formulations, are largely irrelevant here. The pertinent question for any supplement is whether it touches OATP1B1, OATP1B3, or BCRP. Glycine does not appear to do so.

What Is Glycine and Why Do People Take It?

Glycine is the smallest amino acid and the most abundant in collagen. Adults consuming a typical Western diet get roughly 2 to 3 g of glycine per day from food, yet whole-body demand may be closer to 10 g per day when collagen turnover, glutathione synthesis, and bile acid conjugation are accounted for [2]. Supplement doses typically range from 3 to 5 g for sleep support and up to 10 to 15 g for connective-tissue or metabolic goals.

Mechanisms of Action

Glycine acts as an inhibitory neurotransmitter in the spinal cord via glycine receptors and modulates NMDA receptor activity in the brain. These central nervous system effects underlie its sleep-promoting properties. Peripherally, glycine is an obligate substrate for glutathione (via the gamma-glutamylcysteine pathway) and for bile acid conjugation, where it competes with taurine as a conjugate for cholic and chenodeoxycholic acids.

Common Reasons Statin Patients Reach for Glycine

Patients on rosuvastatin are, by definition, managing cardiovascular risk. They often also deal with poor sleep (a cardiovascular risk factor in its own right), insulin resistance, and joint discomfort. Glycine is marketed for all three concerns, which is precisely why the combination comes up so often in clinical conversations.

Is There a Direct Pharmacokinetic Interaction Between Glycine and Rosuvastatin?

No published pharmacokinetic study has demonstrated that glycine alters rosuvastatin plasma concentrations. This absence of evidence is meaningful here because the mechanism would need to be specific: glycine would have to inhibit or induce OATP1B1, OATP1B3, or BCRP to change rosuvastatin exposure.

Transporter Data

Glycine is an endogenous amino acid transported by the sodium-coupled neutral amino acid transporter family (SNAT1, SNAT2) and glycine transporters (GlyT1, GlyT2). None of these overlap functionally with the hepatic organic anion transporters that handle rosuvastatin. An in-silico analysis of glycine's chemical structure, which has a molecular weight of 75.03 Da and no aromatic rings, shows little structural basis for OATP inhibition, which typically requires a more complex hydrophobic scaffold [3].

Protein Binding Considerations

Rosuvastatin is approximately 88 percent protein-bound. Glycine, being a hydrophilic amino acid, does not compete meaningfully for albumin binding sites. Displacement interactions are not expected.

CYP Enzyme Considerations

Glycine does not induce or inhibit CYP1A2, CYP2C9, or CYP3A4 at dietary or supplemental doses. Because rosuvastatin has minimal CYP metabolism anyway, this point is largely academic but worth stating explicitly.

The HealthRX clinical team uses the following three-question screening framework before flagging any supplement-drug pair for the prescriber:

1. Does the supplement inhibit or induce the drug's primary clearance pathway (transporter or enzyme)?
2. Does the supplement produce a pharmacodynamic effect that adds to or counteracts the drug's intended action?
3. Does the supplement affect a lab value or biomarker the prescriber is monitoring?

For glycine plus rosuvastatin, question one receives a "no." Questions two and three receive a "possibly, in specific patient populations," which is addressed in the sections below.

Pharmacodynamic Considerations: Where the Real Conversation Lives

Even without a pharmacokinetic interaction, two substances can still interact pharmacodynamically, meaning they affect the same physiological outcome from different angles. For glycine and rosuvastatin, three areas deserve attention.

Sleep Quality and Cardiovascular Risk

A randomized, placebo-controlled crossover study by Bannai et al. (2012, N=11) found that 3 g of glycine taken before bed reduced subjective sleep-onset latency and improved objective sleep quality as measured by polysomnography, with no serious adverse events [4]. Sleep deprivation independently worsens lipid profiles and raises cardiovascular event risk, so a glycine-driven improvement in sleep could, in theory, complement rosuvastatin's cardiovascular-protective effects. This is not a documented combination but a plausible directional benefit.

Patients on rosuvastatin who also have obstructive sleep apnea or chronic insomnia may find glycine a low-risk option for sleep support while they await evaluation or treatment for the underlying sleep disorder.

Blood Glucose and Insulin Sensitivity

Statins carry an FDA label warning about a small but real increase in fasting blood glucose. A large meta-analysis published in The Lancet (Sattar et al., 2010, 13 trials, N=91,140) found that statin therapy was associated with a 9 percent increase in incident diabetes (OR 1.09, 95% CI 1.02 to 1.17) [5]. Rosuvastatin specifically showed a signal for glucose elevation in the JUPITER trial (N=17,802), where the rosuvastatin group had a 27 percent higher rate of physician-reported diabetes than placebo [6].

Glycine, meanwhile, may have a modest glucose-lowering effect. A randomized trial by Kassi et al. Showed that glycine supplementation improved insulin secretion in patients with metabolic syndrome [7]. Whether this offsets statin-related glucose elevation is speculative, but patients with pre-diabetes or type 2 diabetes on rosuvastatin should monitor fasting glucose if they add glycine, because the net direction could go either way and their prescriber needs accurate data.

Muscle Health and Myalgia

Statin-associated muscle symptoms (SAMS) affect roughly 5 to 10 percent of patients in observational studies, though the SAMSON trial (Wood et al., BMJ, 2020, N=60) found that 90 percent of symptom burden was attributable to nocebo effect [8]. Still, some patients do experience genuine myopathy, marked by creatine kinase elevation above 10 times the upper limit of normal.

Glycine is a direct precursor to creatine (via the arginine-glycine amidinotransferase reaction) and a substrate for glutathione, the cell's primary antioxidant. Theoretically, adequate glycine availability might support mitochondrial health in muscle cells. No clinical trial has tested glycine specifically as a SAMS mitigator. If you are taking rosuvastatin and experiencing muscle aches, report that to your prescriber before adding any supplement.

What the Guidelines Say About Supplement Disclosure

The American College of Cardiology / American Heart Association 2018 Guideline on the Management of Blood Cholesterol states that clinicians should ask about all concomitant medications and supplements at every visit because of the potential for unrecognized interactions [9]. The guideline does not name glycine specifically, but the principle applies: disclose every supplement you take.

The National Lipid Association's 2022 Consensus Recommendations on Patient-Centered Management of Dyslipidemia also advise patients to inform their care team about dietary supplements, particularly those marketed for cardiovascular or metabolic benefits, because some supplements (niacin, red yeast rice, fish oil at prescription doses) have direct lipid effects that alter therapeutic targets [10].

"Patients and clinicians should be aware that dietary supplements are not regulated as drugs, and the potential for interaction with pharmacotherapy, even when low, should prompt a conversation rather than an assumption of safety," according to the NLA 2022 document.

Dose Timing: Does Separation Matter?

For pharmacokinetic interactions, dose separation is a standard risk-reduction strategy. Because no pharmacokinetic interaction has been identified between glycine and rosuvastatin, strict dose separation is not required on mechanistic grounds.

Practical Timing Suggestions

Rosuvastatin can be taken at any time of day with similar efficacy given its 19-hour half-life. Most patients take it in the morning or evening based on personal preference. If you are using glycine for sleep (the most common indication), a 3 g dose 30 to 60 minutes before bed is the protocol used in Bannai et al. [4]. There is no pharmacological conflict with taking rosuvastatin in the morning and glycine at night.

If you are using glycine at higher doses for connective-tissue support, 5 to 10 g with meals is a common approach in research protocols. At those doses, the glycine is largely absorbed before it reaches any tissue compartment that rosuvastatin occupies, and again, transporter overlap is not a concern.

When to Take Both and What to Watch

Take rosuvastatin at your usual consistent time. Add glycine at whatever time aligns with your goal (sleep vs. Daytime collagen synthesis). Check fasting lipids and fasting glucose at your next scheduled lab visit and report any new muscle symptoms to your prescriber promptly.

Special Populations: Who Should Be More Cautious?

Patients with Chronic Kidney Disease

Rosuvastatin clearance is reduced in patients with severe CKD (eGFR <30 mL/min/1.73 m²), and the maximum recommended dose in that group is 10 mg daily per the FDA label [1]. Glycine is renally cleared and accumulates modestly in CKD. While glycine itself is not nephrotoxic, CKD patients already face a higher pill and supplement burden, and any addition warrants a pharmacist review.

Patients with Type 2 Diabetes

As described above, both rosuvastatin and glycine may influence fasting glucose in opposite directions. Diabetic patients should check fasting glucose within 4 to 6 weeks of starting glycine and share results with their prescriber. Target fasting glucose per the American Diabetes Association 2024 Standards of Care is 80 to 130 mg/dL [11].

Patients Already Experiencing SAMS

Adding any supplement to a regimen when statin-associated muscle symptoms are unresolved complicates the clinical picture. Establish a stable, symptom-free baseline before introducing glycine.

Pregnant or Breastfeeding Patients

Rosuvastatin is contraindicated in pregnancy (FDA Category X). If you are pregnant, the entire conversation about which supplements to pair with rosuvastatin is moot because the statin itself should have been discontinued.

What the Interaction Databases Say

The Natural Medicines Comprehensive Database rates the glycine-rosuvastatin combination as having "no known interaction" based on available evidence as of the most recent update. Drugs.com's interaction checker similarly returns no interaction flag. These tools are algorithm-driven and may not capture nuanced pharmacodynamic considerations, but the absence of a flag for a pharmacokinetic interaction is meaningful.

The FDA Adverse Event Reporting System (FAERS) has received no widely reported cluster of adverse events attributed specifically to the glycine-rosuvastatin combination, though FAERS data has the inherent limitations of voluntary reporting and attribution bias.

Monitoring Checklist for Patients Taking Both

If you are currently taking rosuvastatin and want to add glycine, or you are already taking both, use this monitoring checklist at your next provider visit:

• Fasting lipid panel (LDL-C, HDL-C, triglycerides) to confirm rosuvastatin efficacy is unchanged
• Fasting glucose and HbA1c, particularly if you have pre-diabetes or type 2 diabetes
• Creatine kinase if you report new muscle aches, weakness, or dark urine
• Liver function tests if you are taking glycine at doses above 10 g per day for extended periods (hepatic metabolism of large glycine loads generates oxalate, and although clinical hyperoxaluria from dietary glycine is not well-documented, it is a theoretical concern at very high doses)
• Blood pressure, because improved sleep quality from glycine may modestly lower nocturnal blood pressure, which your provider should know about if you are also on antihypertensives

Practical Guidance Summary

Glycine at doses of 3 to 10 g per day does not appear to alter rosuvastatin's pharmacokinetics. The two compounds do not share metabolic pathways in any documented way. The areas requiring attention are pharmacodynamic: glucose regulation in diabetic statin users, sleep-related cardiovascular risk modification, and the theoretical muscle-health angle. Disclose glycine use to your prescriber. Have your fasting labs checked within 6 to 8 weeks of adding any new supplement to a statin regimen.

The American Heart Association recommends that all patients on lipid-lowering therapy maintain regular follow-up laboratory monitoring every 4 to 12 months once at a stable dose [9].