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Tests & Biomarkers Every Dietitian Should Know for Detecting Prediabetes and Diabetes

  • Michelle Britto
  • August 25, 2025

As dietitians, we’re often the first point of contact for people worried about blood sugar, weight gain, or family history of diabetes. While we don’t diagnose, our role in early detection, education, and referral is critical. Understanding the key blood tests and biomarkers helps us interpret results, guide nutrition interventions, and collaborate effectively with physicians.

Core Tests for Prediabetes and Diabetes

  1. Fasting Plasma Glucose (FPG)
  • Prediabetes: 100–125 mg/dL
  • Diabetes: ≥126 mg/dL (confirmed on repeat test)
  • Quick, inexpensive, but can miss post-meal abnormalities.

Pro Tip: Clients with normal fasting glucose but strong risk factors may still benefit from further testing (like OGTT).

  1. Oral Glucose Tolerance Test (OGTT)
  • Prediabetes: 140–199 mg/dL (2-hour value)
  • Diabetes: ≥200 mg/dL
  • Reveals postprandial spikes missed by fasting glucose.

Pro Tip: Useful in women with PCOS or clients with “normal” fasting sugars but symptoms of insulin resistance.

  1. Hemoglobin A1c (HbA1c)
  • Prediabetes: 5.7–6.4%
  • Diabetes: ≥6.5%
  • Reflects average glucose for 2–3 months.

Pro Tip: Great for tracking long-term dietary impact. Educate clients that iron deficiency, kidney disease, and hemoglobin variants can affect results.

Biomarker Tests Beyond Glucose

These tests aren’t always ordered first, but they provide powerful insights for nutrition planning.

  1. Fasting Insulin
  • Elevated levels → early insulin resistance.
  • Benefit: Helps tailor low-glycemic, high-fiber diets before glucose levels rise.
  1. HOMA-IR (Homeostatic Model of Insulin Resistance)
  • Formula using fasting glucose + insulin.
  • Benefit: Identifies insulin resistance in overweight clients with “normal” sugars.
  1. Lipid Profile
  • Prediabetes often comes with atherogenic dyslipidemia: high triglycerides, low HDL, small dense LDL.
  • Benefit: Reinforce omega-3, MUFA, and fiber-rich diets to improve lipid-glucose synergy.
  1. C-Peptide
  • Reflects endogenous insulin production.
  • Benefit: Differentiates between insulin deficiency vs. insulin resistance.
  1. hs-CRP (High-Sensitivity C-Reactive Protein)
  • Elevated levels = systemic inflammation.
  • Benefit: Emphasize anti-inflammatory nutrition (omega-3s, antioxidants, phytonutrients).

When to Recommend Testing

Dietitians should encourage blood sugar and biomarker testing in clients with:

  1. Family history of diabetes
  2. Overweight/abdominal obesity
  3. Hypertension or dyslipidemia
  4. PCOS or gestational diabetes history
  5. Sedentary lifestyle

The ADA recommends screening at age 35, or earlier with risk factors.

On the ReeCoach Dashboard you can now add blood test and biomarker testing as a part of your packages for the clients that fit these risk factors.

Practical Takeaway:

  1. Use FPG, OGTT, and HbA1c as the foundation.
    Incorporate insulin, HOMA-IR, and lipid profile for metabolic risk mapping.
  2. Educate clients on the meaning of results, numbers can feel scary, but they’re a starting point for lifestyle change.
  3. Partner with physicians for referral, but own the space of translating lab values into practical, food-first strategies.
  4. Reework Mind & Body allows your clients to easily book blood tests or upload their reports for you to evaluate and interpret.

Want to collaborate or know more about ReeCoach?

Let’s connect and build the future of nutrition together – Contact us here

References:

  1. American Diabetes Association. Classification and diagnosis of diabetes: Standards of Medical Care in Diabetes—2025. Diabetes Care. 2025;48(Suppl. 1):S15–S33. doi:10.2337/dc25-S002
  2. International Expert Committee. International Expert Committee report on the role of the A1C assay in the diagnosis of diabetes. Diabetes Care. 2009;32(7):1327–1334. doi:10.2337/dc09-9033
  3. Bonora E, Tuomilehto J. The pros and cons of diagnosing diabetes with A1C. Diabetes Care. 2011;34(Suppl 2):S184–S190. doi:10.2337/dc11-S216
  4. Matthews DR, Hosker JP, Rudenski AS, Naylor BA, Treacher DF, Turner RC. Homeostasis model assessment: insulin resistance and β-cell function from fasting plasma glucose and insulin concentrations in man. Diabetologia. 1985;28(7):412–419. doi:10.1007/BF00280883
  5. Emerging Risk Factors Collaboration, Kaptoge S, Di Angelantonio E, et al. C-reactive protein concentration and risk of coronary heart disease, stroke, and mortality: an individual participant meta-analysis. Lancet. 2010;375(9709):132–140. doi:10.1016/S0140-6736(09)61717-7

Latest Blogs

Tests & Biomarkers Every Dietitian Should Know for Detecting Prediabetes and Diabetes

  • Michelle Britto
  • August 25, 2025

As dietitians, we’re often the first point of contact for people worried about blood sugar, weight gain, or family history of diabetes. While we don’t diagnose, our role in early detection, education, and referral is critical. Understanding the key blood tests and biomarkers helps us interpret results, guide nutrition interventions, and collaborate effectively with physicians.

Core Tests for Prediabetes and Diabetes

  1. Fasting Plasma Glucose (FPG)
  • Prediabetes: 100–125 mg/dL
  • Diabetes: ≥126 mg/dL (confirmed on repeat test)
  • Quick, inexpensive, but can miss post-meal abnormalities.

Pro Tip: Clients with normal fasting glucose but strong risk factors may still benefit from further testing (like OGTT).

  1. Oral Glucose Tolerance Test (OGTT)
  • Prediabetes: 140–199 mg/dL (2-hour value)
  • Diabetes: ≥200 mg/dL
  • Reveals postprandial spikes missed by fasting glucose.

Pro Tip: Useful in women with PCOS or clients with “normal” fasting sugars but symptoms of insulin resistance.

  1. Hemoglobin A1c (HbA1c)
  • Prediabetes: 5.7–6.4%
  • Diabetes: ≥6.5%
  • Reflects average glucose for 2–3 months.

Pro Tip: Great for tracking long-term dietary impact. Educate clients that iron deficiency, kidney disease, and hemoglobin variants can affect results.

Biomarker Tests Beyond Glucose

These tests aren’t always ordered first, but they provide powerful insights for nutrition planning.

  1. Fasting Insulin
  • Elevated levels → early insulin resistance.
  • Benefit: Helps tailor low-glycemic, high-fiber diets before glucose levels rise.
  1. HOMA-IR (Homeostatic Model of Insulin Resistance)
  • Formula using fasting glucose + insulin.
  • Benefit: Identifies insulin resistance in overweight clients with “normal” sugars.
  1. Lipid Profile
  • Prediabetes often comes with atherogenic dyslipidemia: high triglycerides, low HDL, small dense LDL.
  • Benefit: Reinforce omega-3, MUFA, and fiber-rich diets to improve lipid-glucose synergy.
  1. C-Peptide
  • Reflects endogenous insulin production.
  • Benefit: Differentiates between insulin deficiency vs. insulin resistance.
  1. hs-CRP (High-Sensitivity C-Reactive Protein)
  • Elevated levels = systemic inflammation.
  • Benefit: Emphasize anti-inflammatory nutrition (omega-3s, antioxidants, phytonutrients).

When to Recommend Testing

Dietitians should encourage blood sugar and biomarker testing in clients with:

  1. Family history of diabetes
  2. Overweight/abdominal obesity
  3. Hypertension or dyslipidemia
  4. PCOS or gestational diabetes history
  5. Sedentary lifestyle

The ADA recommends screening at age 35, or earlier with risk factors.

On the ReeCoach Dashboard you can now add blood test and biomarker testing as a part of your packages for the clients that fit these risk factors.

Practical Takeaway:

  1. Use FPG, OGTT, and HbA1c as the foundation.
    Incorporate insulin, HOMA-IR, and lipid profile for metabolic risk mapping.
  2. Educate clients on the meaning of results, numbers can feel scary, but they’re a starting point for lifestyle change.
  3. Partner with physicians for referral, but own the space of translating lab values into practical, food-first strategies.
  4. Reework Mind & Body allows your clients to easily book blood tests or upload their reports for you to evaluate and interpret.

Want to collaborate or know more about ReeCoach?

Let’s connect and build the future of nutrition together – Contact us here

References:

  1. American Diabetes Association. Classification and diagnosis of diabetes: Standards of Medical Care in Diabetes—2025. Diabetes Care. 2025;48(Suppl. 1):S15–S33. doi:10.2337/dc25-S002
  2. International Expert Committee. International Expert Committee report on the role of the A1C assay in the diagnosis of diabetes. Diabetes Care. 2009;32(7):1327–1334. doi:10.2337/dc09-9033
  3. Bonora E, Tuomilehto J. The pros and cons of diagnosing diabetes with A1C. Diabetes Care. 2011;34(Suppl 2):S184–S190. doi:10.2337/dc11-S216
  4. Matthews DR, Hosker JP, Rudenski AS, Naylor BA, Treacher DF, Turner RC. Homeostasis model assessment: insulin resistance and β-cell function from fasting plasma glucose and insulin concentrations in man. Diabetologia. 1985;28(7):412–419. doi:10.1007/BF00280883
  5. Emerging Risk Factors Collaboration, Kaptoge S, Di Angelantonio E, et al. C-reactive protein concentration and risk of coronary heart disease, stroke, and mortality: an individual participant meta-analysis. Lancet. 2010;375(9709):132–140. doi:10.1016/S0140-6736(09)61717-7

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