Can I Take Glycine with Repatha (Evolocumab)?

What Is Repatha and How Does It Work?

Repatha is a fully human monoclonal antibody that targets proprotein convertase subtilisin/kexin type 9 (PCSK9), a protein that degrades LDL receptors on hepatocytes. By blocking PCSK9, evolocumab keeps more LDL receptors on the liver surface, which pulls LDL-C out of circulation.

The FOURIER trial (N=27,564) demonstrated that evolocumab reduced LDL-C by 59% from baseline and cut the risk of major adverse cardiovascular events (MACE) by 15% over a median follow-up of 2.2 years compared with placebo in patients with established ASCVD already on statin therapy ([1]).

Metabolism and Clearance

Unlike statins, which are processed through hepatic CYP3A4, CYP2C9, or CYP2C8 enzymes, evolocumab follows the same catabolic pathway as endogenous immunoglobulins. It is broken down by ubiquitous proteases throughout the body. Because no cytochrome P450 enzyme is involved, the classic drug-supplement interaction framework (enzyme inhibition or induction) simply does not apply here.

The FDA prescribing information for Repatha confirms no formal pharmacokinetic drug interaction studies were required, and no dose adjustment is needed based on co-administered lipid-lowering drugs or other agents ([2]).

Approved Indications

Evolocumab is FDA-approved for three indications:

• Heterozygous familial hypercholesterolemia (HeFH)
• Homozygous familial hypercholesterolemia (HoFH), at the higher 420 mg monthly dose
• Established atherosclerotic cardiovascular disease (ASCVD) as an adjunct to diet and maximally tolerated statin therapy

The 2022 ACC/AHA Guideline on Cardiovascular Risk Reduction states: "For patients with clinical ASCVD whose LDL-C remains 70 mg/dL or higher on maximally tolerated statin therapy, it is reasonable to add a PCSK9 inhibitor" ([3]).

What Is Glycine and Why Do People Take It?

Glycine is the simplest amino acid structurally and is classified as conditionally non-essential, meaning the body synthesizes roughly 3 g per day endogenously but dietary and supplemental intake may be needed to meet the 15 to 20 g per day total demand estimated in metabolic flux models ([4]).

People supplement glycine for four main reasons: improved sleep quality, joint and skin collagen support, blood glucose modulation, and general anti-inflammatory signaling. Typical supplement doses range from 3 g to 5 g taken before sleep, though some protocols for connective tissue repair use up to 15 g per day split across meals.

Sleep and the Nervous System

Oral glycine (3 g) taken 1 hour before bed reduced subjective and objective sleep-onset time in a randomized crossover study (N=11) published in Sleep and Biological Rhythms, with participants reporting lower fatigue and improved cognitive performance the following morning ([5]). Glycine acts as an inhibitory neurotransmitter in the spinal cord and brainstem, and also lowers core body temperature through peripheral vasodilation, both of which accelerate sleep onset.

Glycemic and Metabolic Effects

Glycine has a glucose-lowering signal in some research contexts. A 2015 clinical study found that glycine supplementation at 5 g three times daily reduced HbA1c by 0.5 percentage points over 14 weeks in patients with type 2 diabetes compared with placebo ([6]). The proposed mechanism involves enhanced glucagon-like peptide-1 (GLP-1) secretion and improved insulin sensitivity via reduced oxidative stress.

For a patient on evolocumab, this matters indirectly. Statin therapy, which most Repatha patients also take, carries a well-documented risk of new-onset type 2 diabetes (OR approximately 1.09 to 1.13 per meta-analysis data), and any supplement that mildly improves insulin sensitivity deserves attention at monitoring visits, though it is not a contraindication ([7]).

Collagen Synthesis

Glycine constitutes approximately one-third of the amino acid residues in collagen. Supplementation at 5 to 15 g per day is commonly used alongside vitamin C and proline to support tendon, cartilage, and skin repair. This use has no meaningful interface with evolocumab's mechanism of action.

Is There a Pharmacokinetic Interaction Between Glycine and Repatha?

No. There is no pharmacokinetic interaction.

Evolocumab does not rely on any transporters or enzymes that glycine modulates. Glycine is absorbed via sodium-coupled neutral amino acid transporters (SNAT1, SNAT2) in the gut and distributed widely as a free amino acid. It does not inhibit or induce CYP1A2, CYP2C9, CYP2C19, CYP2D6, or CYP3A4. Evolocumab is not a substrate of any of these enzymes either ([2]).

Protein Binding Is Not a Concern

Some supplements interact with highly protein-bound drugs by displacing them from albumin or other carriers. Evolocumab, as a large monoclonal antibody (molecular weight approximately 144 kDa), does not circulate as a protein-bound small molecule. Displacement interactions are physically irrelevant at this molecular scale.

Absorption Timing

Evolocumab is delivered subcutaneously, absorbed via lymphatic uptake, and reaches peak serum concentration at approximately 3 to 4 days post-injection. Glycine is taken orally and peaks in plasma within 1 to 2 hours. There is no shared absorption pathway and no competitive interaction at the gut level.

Are There Any Pharmacodynamic Overlaps to Consider?

This is where the analysis requires a bit more nuance. Pharmacodynamic interactions occur when two agents affect the same physiological system, even without sharing a metabolic route.

Lipid Pathway Adjacency

Glycine has been studied for modest effects on lipid metabolism. A small randomized trial (N=60) found that glycine 5 g three times daily over 3 months reduced total cholesterol by approximately 5 mg/dL and triglycerides by approximately 12 mg/dL in patients with metabolic syndrome ([8]). These are small effects. Evolocumab in the same population would reduce LDL-C by 50 to 65%. The glycine effect is directionally aligned (both trend toward lipid benefit) and additive at most, not antagonistic.

No trial has documented glycine blunting the LDL receptor upregulation produced by PCSK9 inhibition. The mechanisms are entirely separate: evolocumab works at the PCSK9 protein level, while glycine's lipid effects appear to involve mitochondrial function and de novo lipogenesis attenuation.

Insulin Sensitivity Overlap With Statin Co-Therapy

Because most evolocumab patients are already taking a high-intensity statin (atorvastatin 40 to 80 mg or rosuvastatin 20 to 40 mg), the statin's modest diabetogenic risk is the relevant backdrop. Glycine's insulin-sensitizing effect at 5 to 15 g per day is unlikely to be harmful here. If anything, it provides a counterweight. A prescriber monitoring HbA1c and fasting glucose in a statin-plus-evolocumab patient does not need to adjust monitoring frequency solely because of glycine, but should note the supplement at the next visit.

Blood Pressure

Repatha does not lower blood pressure directly. Glycine has very modest vasodilatory properties. One small trial (N=26) showed a 2 to 3 mmHg reduction in systolic blood pressure with glycine 5 g per day over 12 weeks ([9]). This effect is not clinically significant in the context of cardiovascular drug regimens, but patients on antihypertensives should mention any new supplements to their prescriber as a matter of routine.

What Does the Evidence Say About Supplement Safety in PCSK9 Inhibitor Patients?

Clinical trial data on supplement combinations specifically in PCSK9 inhibitor populations is sparse. Most guidance extrapolates from mechanistic reasoning and general supplement pharmacology.

The American College of Cardiology's 2023 patient resource on PCSK9 inhibitors notes that patients should disclose all supplements to their cardiologist, not because monoclonal antibody interactions are common, but because the underlying cardiovascular disease burden means any unmonitored physiological change deserves clinical context ([3]).

The HealthRX clinical team uses a three-tier risk classification for supplements in PCSK9 inhibitor patients:

Tier 1 (low concern, typically no action needed): Amino acids (including glycine), most vitamins, magnesium, CoQ10, omega-3 fatty acids at standard doses.

Tier 2 (moderate concern, disclose at next visit): High-dose niacin (1 to 3 g per day), red yeast rice, berberine, high-dose fish oil (above 4 g EPA+DHA daily), and plant sterols above 3 g per day, because these directly target lipid pathways that Repatha is also targeting and may complicate interpretation of lipid panel results.

Tier 3 (discuss before starting): Any supplement that significantly alters coagulation (high-dose vitamin E above 800 IU, nattokinase, high-dose ginkgo) given that ASCVD patients frequently take antiplatelet agents or anticoagulants.

Glycine falls clearly into Tier 1 by this classification.

Dosing and Timing Guidance for Patients Taking Both

Glycine Dose Ranges in Clinical Use

• Sleep optimization: 3 g taken 30 to 60 minutes before bed
• Glycemic support: 3 to 5 g with meals, up to 3 times daily
• Connective tissue/collagen: 5 to 10 g daily, often split between two servings

No dose-separation window from Repatha is required. Because evolocumab is subcutaneous and glycine is oral, they do not share any absorption interface that would require timing adjustments.

Repatha Administration Reminders

Evolocumab is given as:

• 140 mg subcutaneously every 2 weeks, or
• 420 mg (delivered as three 140 mg injections within 30 minutes) once monthly

The SureClick autoinjector or Pushtronex on-body infusor are the two delivery systems. Glycine can be taken on any day of the injection cycle without concern.

Who Should Use Extra Caution?

Patients with chronic kidney disease (CKD) stages 3 to 5 should be aware that glycine is metabolized partly through the kidney, and high-dose glycine (above 10 g per day) may produce modest elevations in serum creatinine in this population. CKD is also common in patients with ASCVD. The prescribing nephrologist or cardiologist should be aware of glycine use at doses above 5 g per day in CKD patients ([10]).

Patients with glycine encephalopathy (non-ketotic hyperglycinemia), a rare inborn error of metabolism, should not supplement with glycine. This condition is typically diagnosed in infancy and would be known by adulthood.

Monitoring: What to Watch When Combining Glycine and Repatha

Lipid Panel

After starting evolocumab, the standard monitoring schedule involves a fasting lipid panel at 4 to 12 weeks, then every 3 to 12 months based on patient stability. Glycine is unlikely to shift these values meaningfully, but if your LDL-C response appears unexpectedly blunted, your prescriber should systematically rule out adherence issues, secondary causes of hypercholesterolemia, and unusual supplement interactions rather than attributing the shortfall to glycine.

Blood Glucose and HbA1c

For patients on high-intensity statins alongside evolocumab, annual fasting glucose or HbA1c monitoring is prudent given the statin-associated diabetes risk established in meta-analyses ([7]). Glycine at 5 to 15 g per day may mildly improve these markers. Tracking them before and 3 months after starting glycine can provide useful data at your next cardiology appointment.

Injection Site Reactions

Evolocumab's most common adverse effect is injection site reaction (erythema, pain, bruising), occurring in approximately 2.4% of patients in FOURIER ([1]). Glycine has no known effect on injection site healing or immune response to monoclonal antibodies.

Special Populations

Patients With Familial Hypercholesterolemia

Patients with HeFH or HoFH often use multiple adjuncts beyond statins: ezetimibe, bempedoic acid, and occasionally LDL apheresis. Glycine presents no known interaction with any of these agents either. The amino acid's glycemic and sleep benefits may be particularly welcome given that HeFH patients are often younger and managing a lifelong condition with significant cardiovascular anxiety.

Older Adults

Adults over 65 commonly take glycine for sleep and joint support. This population is also disproportionately represented among evolocumab users given ASCVD prevalence. Older adults may have reduced renal clearance of glycine metabolites; staying at or below 5 g per day is a reasonable precaution. No dose adjustment to evolocumab is required based on age per the FDA label ([2]).

Patients Who Are Pregnant or Planning Pregnancy

The Repatha prescribing information notes limited human pregnancy data and recommends informing prescribers of pregnancy ([2]). Glycine is generally considered safe in pregnancy at dietary levels, but high-dose supplementation during pregnancy has not been formally studied for safety alongside biologic agents. This combination warrants a direct conversation with the managing obstetrician and cardiologist.

A Note on "Natural" Supplements and Perceived Safety

A common assumption is that because glycine is an amino acid naturally present in food (collagen-rich foods like bone broth, skin-on poultry, and gelatin contain 2 to 5 g per serving), it must be completely inert at supplemental doses. This is mostly true for glycine, but the reasoning is not universally reliable for supplements. The key distinction is dose: a physiologic dose of a nutrient and a pharmacologic dose of the same compound can have meaningfully different effects on drug metabolism or organ function.

For glycine specifically, at doses used in clinical trials (3 to 15 g per day), no toxicity signal has emerged in healthy adults or patients with metabolic syndrome. The European Food Safety Authority reviewed glycine and found no established tolerable upper intake level, indicating that adverse effects were not observed even at high intakes in the available literature ([11]).

Practical Takeaways for Your Next Appointment

Bring a list of every supplement you take, including dose and frequency, to your cardiologist or prescribing clinician. For glycine specifically, note:

• The dose you are using (e.g., 3 g nightly for sleep)
• Why you are using it
• How long you have been taking it

Your prescriber can then document this in your chart, track any changes in your lipid panel or glucose values, and confirm no new interactions exist with any medications added to your regimen in the future. A fasting lipid panel at the 8 to 12 week mark after starting evolocumab remains the single most actionable monitoring step for patients beginning PCSK9 inhibitor therapy ([3]).