Can Blood Sugar and Insulin Dysregulation Impact Fertility? Experts Say Yes.
Insulin resistance affects nearly 40% of Americans aged 18 to 44 and develops when cells are chronically exposed to high levels of insulin.1 When we consume carbohydrates, insulin moves glucose from our blood into our cells to be used for energy. A diet high in refined carbohydrates and sugar causes frequent blood sugar spikes, and the resulting insulin surges cause cells to downregulate their insulin receptors, forcing the body to produce even more insulin to keep up, and creating a vicious cycle.
We often think about insulin resistance as part of significant metabolic dysfunction like type 2 diabetes or obesity, but it can exist on its own for years before showing up on lab work. Insulin resistance has also emerged as a factor in female infertility, disrupting key hormonal pathways involved in reproduction.2,3 If you’re thinking about getting pregnant or already trying, keeping tabs on your blood glucose levels, and your fasting insulin (more on that later), will be an important step in the process.
How exactly does insulin resistance impact fertility?
Insulin resistance is common in polycystic ovarian syndrome (PCOS), and it’s a problem because it stimulates the ovaries to overproduce androgens like testosterone—something already happening in PCOS due to high luteinizing hormone (LH) levels. Together, these hormonal imbalances disrupt follicular development and ovulation, often preventing ovulation altogether.4 But, insulin resistance can impact fertility even without PCOS.5
Egg quality and ovulation
Like women with PCOS, women with insulin resistance have limited follicular development—the months-long process in which a follicle (the fluid-filled sac that houses an immature egg), grows, matures, and prepares the egg for ovulation. Egg quality is largely determined during this process, so when follicular development is impaired, egg quality suffers. Studies have shown that women with insulin resistance also have impaired oocyte maturation—a step that’s critical for ovulation to occur.2
Egg quality is further impaired in women with insulin resistance due to increased oxidative stress and compromised mitochondria, which serve as the powerhouse of the egg. In a study using insulin-resistant mice, eggs showed mitochondrial damage and depleted glutathione, weakening their antioxidant defenses. These mice also showed elevated reactive oxygen species (ROS) and damaged membranes, proteins, and DNA, reducing the eggs’ vitality and developmental potential.2
Endometrial receptivity
Insulin resistance also triggers inflammatory cytokines, TNF-α and IL-6.6 Generally protective as short-term defenses, inflammatory cytokines become destructive when released continuously, driving chronic, low-grade inflammation. Combined with oxidative stress, this inflammation decreases endometrial receptivity, ultimately reducing the success rate of embryo implantation.2 Implantation is further impaired by the secretion of excess androgens from the ovaries—an effect of insulin resistance and hyperinsulinemia.2
Current research has also linked TNF-α and IL-6 with ovarian dysfunction and reduced spermatogenesis, the process in which sperm develop from germ cells in men.6
Insulin resistance as an infertility predictor
The research is clear: women with insulin resistance face a higher risk of infertility, and those with the highest insulin resistance scores have significantly higher infertility rates as compared to women without insulin resistance. A 2025 cross-sectional analysis of 1,100 reproductive-aged women using the National Health and Nutrition Examination Survey (NHANES) 2013-2018 dataset identified several insulin resistance indicators as predictors of infertility risk. The strongest was the Metabolic Score for Insulin Resistance (METS-IR), a composite of fasting glucose, triglycerides, BMI, and HDL cholesterol.2 Rather than measuring insulin resistance directly, METS-IR combines these markers to capture blood glucose, blood lipid levels, and body composition for a broader picture of insulin resistance dysregulation.6 Women in the highest METS-IR quartile had 4.48 times the odds of infertility compared to the lowest.2 A second study of ~2,000 women analyzed METS-IR as a predictor of infertility using NHANES data from 2013-2020, reporting a similar pattern, with women in the highest METS-IR quartile associated with greater odds of infertility as compared to the lowest quartile. This association weakened after adjusting for factors like waist circumference.6
How do you know if you’re insulin resistant?
Watch for metabolic syndrome
Metabolic syndrome is a cluster of symptoms that point to blood sugar dysregulation. It is often used synonymously with insulin resistance and prediabetes because it reflects a loss of insulin sensitivity.7 The American Heart Association defines it using the following:
- Abdominal obesity: Waist circumference greater than 40” in men or greater than 35” in women
- High triglycerides: 150 mg/dL or greater
- Low HDL Cholesterol: less than 40 mg/dL in men or 50 mg/dL in women.
- High blood pressure: Systolic 130 mm Hg or greater, or diastolic 85 mm Hg or greater
- High fasting glucose: 100 mg/dL or greater.8
Testing
Some of the below markers are used conventionally used to screen for and diagnose diabetes, which is not our goal. Instead, we’re using their optimal ranges for early signs that your body is working harder than it should to keep blood sugar in check. Insulin resistance can build for years while standard lab results still read “normal”, so we’re after early signs, not a diagnosis. Always interpret results with a qualified healthcare provider.
- Fasting Insulin: Measures insulin in blood after an 8-hour fast, minimum. This is the preferred functional medicine test for insulin resistance as it can detect insulin resistance long before glucose-based tests. It isn’t used to diagnose diabetes, and it still isn’t considered “standard” in many conventional circles.
o Functional/optimal target: ~5 μIU/mL, with the risk for prediabetes doubling at 8 μIU/mL9
- Hemoglobin A1C (HbA1C): Measures how much blood glucose is attached to hemoglobin in red blood cells (glycation). Because red blood cells live about 3 months, HbA1C reflects average blood glucose over that period. A standard diagnostic test, widely used for diabetes.
o Standard Diagnostic Ranges:
§ Normal / Non-Diabetic: Below 5.7%
§ Prediabetes: 5.7% to 6.4%
§ Diabetes: 6.5% or higher10
o Optimal/Functional Ranges:
§ Optimal: 4.1 to 5.7%11
- Fasting Plasma Glucose (FPG): Checks blood glucose levels after an 8-hour fast minimum, usually taken first thing in the morning8. Used to diagnose diabetes.
o Standard Diagnostic Ranges:
§ Normal: 70 to 99 mg/dL
§ Prediabetes: 100 to 125 mg/dL
§ Diabetes: 126 mg/dL or higher (on two separate tests)10
o Functional Ranges:
§ Optimal: 72 to 85 mg/dL (or up to 90 mg/dL)
§ Suboptimal (Risk of Insulin Resistance): 86 to 99 mg/dL12
- METS-IR (Metabolic Score for Insulin Resistance): A calculated score estimating insulin resistance from fasting glucose, a standard lipid panel, and BMI. METS-IR is consistently linked to higher infertility risk, and the marker most directly linked to fertility predictions.6 While there is no set range, infertility risk rises as METS-IR climbs toward ~50, where the association is the strongest2,6
o Use the MDCalc METS-IR calculator to get your score.13
What can you do about it?
Reversing insulin resistance is the standard of care medical treatment for PCOS, and for insulin resistance-associated infertility. Nutrition therapy is a great first-line strategy for better blood glucose and insulin control.14
Nutrition strategies for insulin resistant-associated infertility:
- Minimize refined and high-glycemic carbohydrates. Refined carbs like white bread, sugary drinks, sweets, and refined flour cause the sharpest blood glucose and insulin spikes. Cutting back on these foods, while focusing on fiber-rich, whole-food sources like vegetables, legumes, and some whole grains is the first and best strategy.15,16
- Pair protein and fat with every meal/snack. Dietary protein and fat stabilize blood glucose, preventing the insulin spikes that feed the vicious cycle.17
- Consider berberine. Berberine improves insulin sensitivity. Found in barberry, goldenseal, and Oregon grape root.18
Insulin resistance can impair fertility even in women without PCOS or other obvious metabolic diagnoses, including lean women.14 If you suspect you’re insulin resistant, dietary changes are a great first step, and simple testing can help you catch it early. Always work with a licensed medical practitioner to interpret test results and to build a plan that’s right for you.
References
1. Parcha V, Heindl B, Kalra R, et al. Insulin Resistance and Cardiometabolic Risk Profile Among Nondiabetic American Young Adults: Insights From NHANES. The Journal of Clinical Endocrinology & Metabolism. 2022;107(1):e25-e37. doi:10.1210/clinem/dgab645
2. Yan R, Zhang J, Ma H, Wu Y, Fan Y. Potential of seven insulin resistance indicators as biomarkers to predict infertility risk in U.S. women of reproductive age: a cross-sectional study. Reprod Biol Endocrinol. 2025;23(1):77. doi:10.1186/s12958-025-01416-wAshraf
3. Ding H, Zhang J, Zhang F, et al. Resistance to the Insulin and Elevated Level of Androgen: A Major Cause of Polycystic Ovary Syndrome. Front Endocrinol. 2021;12:741764. doi:10.3389/fendo.2021.741764
4. Lei R, Chen S, Li W. Advances in the study of the correlation between insulin resistance and infertility. Front Endocrinol. 2024;15:1288326. doi:10.3389/fendo.2024.1288326
5. Wang H, Zhang Y, Fang X, Kwak-Kim J, Wu L. Insulin Resistance Adversely Affect IVF Outcomes in Lean Women Without PCOS. Front Endocrinol. 2021;12:734638. doi:10.3389/fendo.2021.734638
6. Li X, Sun Q, Zhang J, Ling X, Liu Y, Zhao C. Association Between Metabolic Score for Insulin Resistance (METS-IR) and Risk of Infertility: Evidence from NHANES 2013–2020 and Mendelian Randomization Study. IJWH. 2026;Volume 18:1-15. doi:10.2147/IJWH.S575111
7. What is metabolic syndrome? www.heart.org. October 17, 2023. Accessed August 4, 2026. https://www.heart.org/en/health-topics/metabolic-syndrome/about-metabolic-syndrome.
8. Symptoms and diagnosis of metabolic syndrome. www.heart.org. October 17, 2023. Accessed August 4, 2026. https://www.heart.org/en/health-topics/metabolic-syndrome/symptoms-and-diagnosis-of-metabolic-syndrome.
9. Johnson JL, Duick DS, Chui MA, Aldasouqi SA. Identifying Prediabetes Using Fasting Insulin Levels. Endocrine Practice. 2010;16(1):47-52. doi:10.4158/EP09031.OR
10. Diabetes diagnosis. Diabetes Diagnosis & Tests | ADA. Accessed August 4, 2026.https://diabetes.org/about-diabetes/diagnosis.
11. Weatherby D, Ferguson S. Blood Chemistry and CBC Analysis -- Clinical Laboratory Testing from a Functional Perspective: Quick Reference Guide. Bear Mountain Publishing ; Weatherby & Associates, LLC dist.; 2005. (functional a1c)
12. Tirosh A, Shai I, Tekes-Manova D, et al. Normal Fasting Plasma Glucose Levels and Type 2 Diabetes in Young Men. N Engl J Med. 2005;353(14):1454-1462. doi:10.1056/NEJMoa050080
13. Metabolic Score for Insulin Resistance (METS-IR). MDCalc. 2026. Accessed August 5, 2026. https://www.mdcalc.com/calc/10181/metabolic-score-insulin-resistance-mets-ir#why-use.
14. Lei R, Chen S, Li W. Advances in the study of the correlation between insulin resistance and infertility. Front Endocrinol. 2024;15:1288326. doi:10.3389/fendo.2024.1288326
15. Schipper MC, Boxem AJ, Blaauwendraad SM, Mulders AGMGJ, Jaddoe VWV, Gaillard R. Associations of periconception dietary glycemic index and load with fertility in women and men: a study among couples in the general population. BMC Med. 2024;22(1):499. doi:10.1186/s12916-024-03718-z
16. Cristodoro M, Zambella E, Fietta I, Inversetti A, Di Simone N. Dietary Patterns and Fertility. Biology. 2024;13(2):131. doi:10.3390/biology13020131
17. Nesti L, Mengozzi A, Tricò D. Impact of Nutrient Type and Sequence on Glucose Tolerance: Physiological Insights and Therapeutic Implications. Front Endocrinol. 2019;10:144. doi:10.3389/fendo.2019.00144
18. Li MF, Zhou XM, Li XL. The Effect of Berberine on Polycystic Ovary Syndrome Patients with Insulin Resistance (PCOS‐IR): A Meta‐Analysis and Systematic Review. Liu IM, ed. Evidence-Based Complementary and Alternative Medicine. 2018;2018(1):2532935. doi:10.1155/2018/2532935
The information in this article is for educational purposes only and should not replace professional advice. Always consult with a qualified expert to determine what services, if any, are right for you.
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