Can I Take Glycine with Farxiga (Dapagliflozin)?

What Is Dapagliflozin and How Does It Work?

Dapagliflozin (Farxiga, AstraZeneca) is an oral sodium-glucose cotransporter-2 (SGLT2) inhibitor. It blocks glucose reabsorption in the proximal renal tubule, causing the kidneys to excrete approximately 70 grams of glucose in urine each day, which lowers blood sugar independent of insulin [1]. This mechanism also produces mild osmotic diuresis and reduces body weight.

FDA-Approved Indications

The FDA has approved dapagliflozin for three distinct indications [2]:

• Type 2 diabetes mellitus (T2DM), as an adjunct to diet and exercise
• Heart failure with reduced ejection fraction (HFrEF) and, since 2022, heart failure with preserved ejection fraction (HFpEF)
• Chronic kidney disease (CKD) with or without T2DM

The DECLARE-TIMI 58 trial (N=17,160) demonstrated that dapagliflozin reduced the composite of cardiovascular death or worsening heart failure by 17% versus placebo (HR 0.83, 95% CI 0.73 to 0.95) [3]. The DAPA-CKD trial (N=4,304) showed a 39% relative risk reduction in the composite kidney endpoint [4].

Common Adverse Effects to Keep in Mind

Genital mycotic infections affect roughly 8% of women and 3% of men taking dapagliflozin [2]. Urinary tract infections (UTIs) occur at a rate approximately 4 percentage points above placebo in pooled trials [3]. Volume depletion and a small increase in LDL-C are also reported. These baseline risks matter when evaluating any supplement that is renally excreted, including glycine.

What Is Glycine and Why Do People Supplement It?

Glycine is the simplest amino acid and the most abundant residue in collagen. Adult humans synthesize roughly 3 g/day endogenously, yet estimated dietary needs for collagen maintenance may reach 10 g/day, suggesting a gap that supplementation could address [5]. The body uses glycine as a precursor for glutathione, creatine, heme, bile acids, and several neurotransmitters.

Sleep and Neurological Uses

One randomized crossover trial (N=11) found that 3 g of glycine taken 1 hour before bed reduced subjective fatigue and improved sleep quality scores on the St. Mary's Hospital Sleep Questionnaire [6]. A follow-up study published in Sleep and Biological Rhythms (N=19) replicated the fatigue-reduction finding [6]. These trials are small, but they drive heavy consumer interest in glycine as a nightly sleep supplement.

Collagen and Connective Tissue Uses

Collagen hydrolysate products are largely glycine by mass. A 24-week randomized trial published in the British Journal of Sports Medicine (N=147) found that 15 g of gelatin (rich in glycine and hydroxyproline) taken with vitamin C increased collagen synthesis markers by 17% versus placebo [7]. Athletes recovering from tendon injuries and patients with osteoarthritis are the primary users.

Metabolic and Glycemic Uses

Glycine's metabolic role is where the Farxiga interaction becomes clinically relevant. Plasma glycine levels are consistently lower in individuals with insulin resistance and type 2 diabetes compared with metabolically healthy controls [8]. This observation has driven interest in glycine as a glucose-modulating supplement.

Does Glycine Affect Blood Glucose?

Yes, glycine appears to have a modest glucose-lowering effect, primarily through stimulating glucagon-like peptide-1 (GLP-1) and insulin secretion. This is where the pharmacodynamic overlap with dapagliflozin sits.

Mechanism: GLP-1 and Insulin Secretion

Glycine acts on glycine receptors expressed in intestinal L-cells and pancreatic alpha and beta cells. A randomized crossover trial in 15 healthy adults found that oral glycine (5 g) taken before a 75 g oral glucose load significantly reduced the incremental area under the glucose curve compared with placebo, an effect partially attributed to enhanced GLP-1 secretion [9]. Dapagliflozin works through a completely separate renal mechanism, so the two agents do not compete at the same receptor or transporter.

Postprandial Glucose Data

A pilot randomized controlled trial in 60 adults with T2DM found that 3 g of glycine consumed before each of three daily meals for 12 weeks reduced fasting plasma glucose by 5.1 mg/dL and 2-hour postprandial glucose by 14.3 mg/dL compared with placebo [10]. These are modest reductions, but they compound with the 70 g/day of urinary glucose lost via dapagliflozin.

Is the Combined Effect Dangerous?

For most patients on dapagliflozin monotherapy, the additional glucose lowering from glycine is unlikely to cause clinically significant hypoglycemia. Dapagliflozin alone carries a low intrinsic hypoglycemia risk because it does not stimulate insulin secretion [2]. The concern rises meaningfully if the patient is also taking insulin, a sulfonylurea (glipizide, glimepiride, glyburide), or a GLP-1 receptor agonist. In those cases, the prescriber should be notified before glycine supplementation begins, and self-monitoring of blood glucose should increase.

Pharmacokinetic Interaction: Does Glycine Change How Farxiga Is Absorbed or Metabolized?

No clinically significant pharmacokinetic interaction has been identified. Dapagliflozin is metabolized primarily by UGT1A9 (uridine 5'-diphospho-glucuronosyltransferase 1A9) in the liver and kidneys, with minor contributions from UGT2B4 [2]. Glycine is not an inhibitor or inducer of UGT1A9 in published literature and does not affect cytochrome P450 enzymes relevant to dapagliflozin clearance [11].

Protein Binding and Volume of Distribution

Dapagliflozin is approximately 91% protein-bound [2]. Glycine, as a free amino acid, does not compete for albumin binding sites in a clinically meaningful way at typical supplemental doses of 3 to 10 g. No displacement interaction is expected.

Renal Excretion Considerations

Both dapagliflozin's active metabolite (dapagliflozin 3-O-glucuronide) and free glycine are eliminated renally [2, 11]. In patients with moderate-to-severe CKD (eGFR <45 mL/min/1.73 m²), glycine clearance may slow, raising plasma glycine exposure, though this effect has not been studied in combination with dapagliflozin specifically. The FDA label contraindicates dapagliflozin for dialysis patients [2]. Patients with CKD who wish to supplement glycine should raise the question with their nephrologist.

UTI Risk: Does Glycine Worsen Farxiga's Urinary Tract Effects?

This is a reasonable concern. Dapagliflozin increases urinary glucose, which can promote bacterial growth and raises UTI risk by roughly 4 percentage points over placebo in clinical trial data [3]. Glycine itself is a nutrient that bacteria can metabolize, and it is excreted in urine after supplementation.

What the Data Actually Show

No published trial has directly examined glycine supplementation and UTI incidence in SGLT2-inhibitor users. A review of amino acid urinary excretion patterns suggests that glycine's urine concentrations after typical 3 to 10 g supplemental doses remain within the normal physiologic range and are unlikely to provide a substantial additional substrate for uropathogens beyond what glucose already provides [11]. Still, the absence of data is not the same as confirmed safety. Patients with recurrent UTIs on dapagliflozin should discuss glycine use with their provider before starting.

Practical Steps to Reduce UTI Risk

• Stay well hydrated: at least 2 liters of water daily
• Urinate after sexual activity
• Report dysuria, frequency, or cloudy urine promptly
• Consider a urine culture if symptoms develop, rather than waiting

Glycine for Sleep While on Farxiga: Any Added Concerns?

Sleep quality is frequently disrupted in patients with type 2 diabetes and heart failure, the two largest Farxiga-using populations [12]. Glycine's proposed sleep benefit (3 g before bed) makes it attractive in these groups.

Nocturnal Hypoglycemia Watch

Dapagliflozin does not independently cause nocturnal hypoglycemia in monotherapy. Adding glycine's mild insulin-secretagogue effect overnight adds a theoretical but small risk, most relevant if the patient also uses bedtime insulin. A continuous glucose monitor (CGM) or pre-sleep fingerstick for 2 to 4 weeks after starting glycine is a reasonable precaution in insulin users.

Volume Status and Nocturia

Dapagliflozin's diuretic effect may cause nocturia in some patients. Glycine taken at night does not worsen diuresis. The two have no overlapping mechanism on fluid handling. Nocturia from dapagliflozin typically improves after 4 to 6 weeks as intravascular volume re-equilibrates [13].

Collagen Supplementation in Diabetic Patients: Glycine's Potential Benefits

Diabetes accelerates the accumulation of advanced glycation end-products (AGEs) in collagen, stiffening tendons and vascular walls [14]. Glycine supplementation at 10 to 15 g/day has been proposed as a strategy to maintain collagen synthesis rates and counteract this glycation-driven degradation.

A practical clinical decision framework for dapagliflozin patients asking about glycine:

1. Monotherapy (dapagliflozin only): Glycine at 3 to 10 g/day is likely safe. Monitor fasting glucose and HbA1c at the next scheduled visit.
2. Dapagliflozin plus insulin or sulfonylurea: Discuss with prescriber first. Increase self-monitoring frequency for 2 to 4 weeks after starting glycine.
3. Dapagliflozin plus CKD (eGFR <45): Consult nephrology before adding any amino acid supplement due to altered clearance.
4. Recurrent UTI history: Weigh the modest theoretical urothelial substrate risk against the benefit; discuss with prescriber.
5. Sleep-focused use (3 g at bedtime): Acceptable in most patients; insulin users should check pre-sleep glucose for the first 2 weeks.

Evidence on Glycine and AGEs

A 2019 study in Nutrients (N=84 adults with metabolic syndrome) found that 15 g/day of glycine for 15 weeks significantly reduced plasma malondialdehyde and improved the GSH/GSSG ratio, indicating reduced oxidative stress [15]. Reduced oxidative stress is mechanistically relevant to slowing AGE formation, though a direct reduction in collagen AGEs was not measured in that trial.

Dapagliflozin's Own Anti-Fibrotic Effects

Dapagliflozin itself reduces cardiac and renal fibrosis markers in animal models and in subgroup analyses of DAPA-CKD [4]. Glycine's collagen-supportive role could be complementary rather than redundant in heart failure or CKD patients. No direct combination trial exists.

Monitoring Plan for Patients Taking Both

Patients who decide to take glycine alongside dapagliflozin should follow a straightforward monitoring schedule.

Glucose Monitoring

Check fasting plasma glucose within 4 to 6 weeks of starting glycine. If HbA1c is due within 3 months, no additional testing is needed beyond the routine schedule. Patients using CGM should review their time-in-range data after 2 weeks.

Symptom-Based Monitoring

Report to the prescriber if any of the following develop within 4 weeks of starting glycine:

• Increased urinary frequency, urgency, or burning (possible UTI)
• Symptoms of hypoglycemia: sweating, tremor, confusion (most relevant in insulin users)
• Significant gastrointestinal discomfort (glycine is generally well-tolerated at 3 to 10 g but can cause nausea at higher doses in sensitive individuals)

Lab Follow-Up

Routine HbA1c every 3 months is recommended by the American Diabetes Association Standards of Care for patients not at goal [16]. A basic metabolic panel to assess eGFR and electrolytes is already standard for dapagliflozin users and does not need to be added specifically for glycine.

What Do Clinicians and Guidelines Say?

The 2024 American Diabetes Association Standards of Medical Care in Diabetes states: "There is insufficient evidence to support the routine use of micronutrients or herbal supplements for glycemic management in people with diabetes, and there may be safety concerns with some products" [16]. Glycine is not explicitly listed as contraindicated, but the guideline's caution about unproven supplements applies.

The ADA further notes that SGLT2 inhibitors "are associated with a low risk of hypoglycemia when used as monotherapy" [16], which supports the assessment that adding glycine to dapagliflozin without other secretagogues carries a low hypoglycemia burden.

A 2021 systematic review in Diabetes, Obesity and Metabolism that examined dietary amino acid supplementation in T2DM concluded that glycine "showed the most consistent evidence of postprandial glucose attenuation among the amino acids reviewed," though the authors noted that all trials were small and short in duration [9].

Practical Dosing Guidance

No established glycine dose exists for glucose management. The doses used in clinical trials range from 3 g (sleep, single pre-bedtime dose) to 15 g/day (collagen synthesis and oxidative stress). For patients on dapagliflozin:

• Sleep: 3 g, 30 to 60 minutes before bed. This is the dose with the best tolerability data [6].
• Collagen support: 10 to 15 g/day in 2 to 3 divided doses with meals.
• Glycemic adjunct: 3 to 5 g before each meal, based on the pilot RCT data [10].

Powder forms dissolve easily in water and are tasteless. Capsule forms are convenient at lower doses. No dose-separation window from dapagliflozin is required based on current pharmacokinetic data, since the two compounds do not compete for the same absorptive or metabolic pathways [2, 11].