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Postprandial glucose reflects levels reached following a meal. An inability to return blood glucose to premeal levels within 2 hours indicates glucose dysregulation. Postprandial glucose won’t be reflected in fasting glucose or HbA1C results.
However, extreme postprandial variations or “excursions” in blood glucose are detrimental and should be identified and addressed when considering overall glycemic control. A good rule of thumb is to limit post-prandial glucose increases to no more than 40 mg/dL (2.22 mmol/L) above fasting or a maximum level below 140 mg/dL (7.77 mmol/L).
Low post-prandial glucose may be associated with excess insulin, malabsorption, or hypothyroidism, while elevated post-prandial glucose may be associated with diabetes mellitus, acute stress, hyperthyroidism, liver disease, or medication side effects.
Standard Range: Less than 140 mg/dL (7.77 mmol/L)
The ODX Range: 110-125 mg/dl (6.11 -6.94 mmol/L)
Low postprandial glucose may be associated with insulin overdose, insulinoma, malabsorption or maldigestion, hypothyroidism, hypopituitarism, or Addison’s disease (Pagana 2022).
High postprandial glucose is associated with diabetes mellitus, acute stress, smoking, corticosteroid therapy, diuretic therapy, hyperthyroidism, liver disease, chronic renal failure, Cushing syndrome, glucagonoma, acromegaly, pheochromocytoma, or poor nutrition (Pagana 2022). Elevated levels are also a risk factor for endothelial dysfunction, inflammation, oxidative stress, cardiovascular disease, retinopathy, all-cause mortality (Madsbad 2016), and cancer (Lu 2019).
The content and quantity of a meal influence the timing and amount of glucose released into the blood. However, glucose levels should return to premeal levels within 2 hours. Postprandial glucose (PPG) can vary but should not remain elevated as long as insulin responds and reduces levels. A 2-hour PPG above 140 mg/dL (7.77 mmol/L) is highly suspected for diabetes and should be investigated further, e.g., with a glucose tolerance test. A level exceeding 140 mg/dL after one hour may indicate gestational diabetes (Pagana 2022).
Evaluating post-prandial glucose may be preferred to HbA1C for identifying compromised glucose control. A 2-hour PPG above 160 mg/dL (8.89 mmol/L) was observed repeatedly in type 2 diabetics despite being considered in “good control” with an HbA1C below 7% (Bonora 2006).
Postprandial hyperglycemia is a risk factor for CVD and events; increased carotid intima-media thickness, carotid artery stenosis, microvascular complications, cognitive dysfunction, cancer, and all-cause mortality. Research suggests that a 1% reduction in PPG in those with HbA1C of 6.5% or higher may reduce the relative risk of myocardial infarction by 14% and the risk of microvascular complications by 37%. Cancer risk was significantly greater in subjects with a two-hour PPG of 200 mg/dL (11.1 mmol/L) or greater (Madsbad 2016).
Isolated “excursions” of hyperglycemia are not reflected in fasting glucose or HbA1C testing though they may indicate an increased risk of diabetes. Hypertension, dyslipidemia, elevated ALT, and microalbuminuria were significantly more prevalent in individuals diagnosed with T2DM by 2-hour PPG alone. A 1-hour PPG may also reveal an increased risk of diabetes when levels are 155 mg/dL (8.6 mmol/L) or higher (Bergman 2020).
Even tighter glucose control may be needed to prevent progression to T2DM. A review of NHANES data revealed that a single random blood glucose (RBG) of 100 mg/dL (5.6 mmol/L) or above was more strongly associated with undiagnosed diabetes than traditional risk factors, including hypertension, BMI, cardiovascular disease, or family history of diabetes. Mean RBG in those with no diabetes was 89.9 mg/dL (5.0 mmol/L), 99.1 mg/dL (5.5 mmol/L) with undiagnosed diabetes, and 156 mg/dL (8.7 mmol/L) in those with undiagnosed diabetes (Bowen 2015).
Lifestyle changes, increasing exercise and activity, and nutrition intervention can improve PPG. Walking after meals and even short intervals of activity throughout the day versus being sedentary improves PPG and insulin levels in those who are overweight or obese (Dunstan 2012).
The order in which foods are consumed during a meal affects PPG as demonstrated in a small study of 11 individuals with type 2 diabetes. When protein and vegetables were consumed first and carbohydrates last, PPG and insulin levels decreased significantly. The 1-hour PPG was 199.4 mg/dL (11.07 mmol/L) when 68 grams of carbohydrate were consumed first versus 125.6 mg/dL (6.97 mmol/L) when the same amount of carbohydrate was consumed last. The 2-hour PPG was 169.2 mg/dL (9.39 mmol/L) versus 140.8 mg/dL (7.8 mmol/L) with carbohydrates last (Shukla 2015).
Soluble dietary fiber also helps reduce the postprandial glucose response (Cassidy 2018). Even meal timing may affect PPG. A meta-analysis also suggests that postprandial glucose response is lower for the same meal during the day versus at night (Leung 2020).
Bonora, E et al. “Prevalence and correlates of post-prandial hyperglycemia in a large sample of patients with type 2 diabetes mellitus.” Diabetologia vol. 49,5 (2006): 846-54. doi:10.1007/s00125-006-0203-x
Bowen, Michael E et al. “Random blood glucose: a robust risk factor for type 2 diabetes.” The Journal of clinical endocrinology and metabolism vol. 100,4 (2015): 1503-10. doi:10.1210/jc.2014-4116
Cassidy, Yvonne M., Emeir M. McSorley, and Philip J. Allsopp. "Effect of soluble dietary fiber on postprandial blood glucose response and its potential as a functional food ingredient." Journal of functional foods (2018).
Dunstan, David W et al. “Breaking up prolonged sitting reduces postprandial glucose and insulin responses.” Diabetes care vol. 35,5 (2012): 976-83. doi:10.2337/dc11-1931 Leung, Gloria K W et al. “Time of day difference in postprandial glucose and insulin responses: Systematic review and meta-analysis of acute postprandial studies.” Chronobiology international vol. 37,3 (2020): 311-326. doi:10.1080/07420528.2019.1683856
Madsbad, Sten. “Impact of postprandial glucose control on diabetes-related complications: How is the evidence evolving?.” Journal of diabetes and its complications vol. 30,2 (2016): 374-85. doi:10.1016/j.jdiacomp.2015.09.019
Pagana, Kathleen Deska, et al. Mosby's Diagnostic and Laboratory Test Reference. 16th ed., Mosby, 2022.
Shukla, Alpana P et al. “Food Order Has a Significant Impact on Postprandial Glucose and Insulin Levels.” Diabetes care vol. 38,7 (2015): e98-9. doi:10.2337/dc15-0429