Why your blood sugar might not be so “normal” after all
Updated: Feb 8
Common tests ordered by your primary care doctor are not adequate to examine blood sugar regulation
Other tests including A1C, Glycomark™, and C-peptide (or insulin) are important to understand how your body regulates blood sugar and to develop a personalized treatment plan
Continuous glucose monitoring is the gold standard to assess blood sugar regulation
As a functional medicine provider, I see patients who are wanting to address the root cause of their health concerns. As such, a proper and thorough assessment of metabolic health is crucial. We know that blood sugar control (or lack thereof) affects all sorts of things such as gut health, autoimmunity, and brain health (i.e. Alzheimer’s is now considered “Type 3 Diabetes”).
What I’ve come to appreciate is how the conventional fasting glucose ordered at your annual physical is just the tip of the iceberg when it comes to gaining a clear understanding of how your body is truly handling blood sugar.
What I hope to do in this article is to shed some light on some additional tests you can ask your functional medicine provider about and briefly explain what I believe to be the best test of all.
What it tells us: average blood sugar over the course of the last 3-4 months
Target values: 5.0-5.3%
What it is: Under situations of high blood sugar, the red blood cells (RBCs) undergo a process called glycation. I explain this to my patients like how onions are caramelized. In the same way, RBCs can become “sweetened” in a process where sugar gets stuck onto the proteins surrounding the RBCs. The more blood sugar is around, the more glycation is going to occur.
Since RBCs live for an average of 3-4 months, this value gives us an idea of average blood sugar over that timeframe.
Most studies looking at mortality (death) data show a U-shaped curve, meaning both high and low A1C values are associated with higher rates of death from any cause. The catch is that good blood sugar control can lead to longer-lived RBCs, and thus, falsely high A1C values. Similarly, poor blood sugar control can lead to immature RBC death and falsely low A1C values. You can calculate the average RBC lifespan by also getting reticulocytes, which are the levels of immature RBCs. This is why further testing is warranted.
What it tells us: blood sugar fluctuations after meals
Target values: 15-30
What it is: Glycomark™ is the tradename for 1-5-Anhydroglucitol (1,5-AG). This is a natural monosaccharide (simple sugar) found in food that is not metabolized in the body. Our kidneys normally filter and reabsorb this sugar. However, when blood sugar levels go above 180 mg/dL after you eat a meal, this sugar gets excreted into the urine, which leads to lower blood levels. Therefore, this test offers insight into the “glycemic variability”, or blood sugar fluctuations, after meals in the last 2 weeks prior of the test. The lower the level of Glycomark
Glycomark™ is essentially measuring your body’s ability to produce a big surge in insulin after a meal. A poor insulin response leads to rapid increases in blood sugar and thus, low Glycomark™ values. It’s a valuable test to get in my clinic as it can pick up on diabetes processes decades before it conventionally gets diagnosed. Some recent research points to how Glycomark™ is superior to A1C. In other words, it’s worse to have normal average blood sugar (average A1C) with high blood sugar swings (low Glycomark™) than it is to have chronically elevated blood sugar (high A1C).
What it tells us: how hard your body is working to maintain blood sugar control
for C-peptide: 1.1-1.8 ng/mL
for insulin: 1-7 microIU/mL
What it is: As you may already know, insulin’s role is to lower blood sugar values. It does this mainly by reducing liver production of glucose. C-peptide is released in a 1:1 ratio with insulin, meaning that for every molecule of insulin released, the same amount of C-peptide is released along with it. C-peptide is a better marker than insulin in that it is not cleared by the liver and lasts longer than insulin does. This gives a more accurate depiction of how hard the body is working to control blood sugar. One paper noted that “C-peptide predicted cardiovascular death even in subjects with normoglycemia [normal blood sugar] and those without metabolic syndrome [don’t have diabetes].”1
Continuous Glucose Monitoring- the “Gold Standard”
What it tells us: precise, in-time evaluation of blood sugar and how different meal compositions affect blood sugar levels.
No more than 50 mg/dL rise in blood sugar at any time after a meal
Less than 140 mg/dL 1 hour after a meal
Less than 120 mg/dL 2 hours after a meal
What it is: This is a small device worn typically on the upper arm that measures blood sugar levels at regular moment throughout the day. These devices are usually worn for a period of 2 weeks which is adequate time to assess how your diet and lifestyle impacts your blood sugar levels. For example, you might see that you do really well with potatoes but not rice, or vice versa. Interestingly, researchers in Israel saw a dramatic variability of how each person’s blood sugar responds to their food.2 Unfortunately, CGMs are usually not covered by insurance unless you have severe diabetes. However, I am encouraged by work by the folks over at Levels to increase access to these devices for direct-consumer use.
Formulating a precision medicine protocol for blood sugar control
Now let’s discuss what to do with all this information. Here’s an outline of how I synthesize all these values into a treatment plan for a patient.
First look at Glycomark™. If below 15, then they have poor insulin response after a meal. We will work on diet, macronutrient ratios, movement after meals, and things that stimulate that initial insulin response.
If A1C is above 5.3% but below 5.7%, most can get away with just regular movement, diet, proper macronutrient ratios. Some may need additional help with lipoic acid and berberine. If above 5.7%, then you are technically prediabetic and would follow the same as the low Glycomark™ protocol with the addition of interventions to support liver health to prevent Non-Alcoholic Fatty Liver Disease (NAFLD) which is present in about a third of Americans and 90% of those who are overweight.
Look at C-peptide (or insulin). If above the cutoffs outlined above with high or low A1C, then the body is insulin resistant. If this is the case, then I work with patients to improve insulin sensitivity with a lower carb, higher protein diet along with interventions that support mitochondria health.
If I have identified an issue with blood sugar control with any of these above values, then I will utilize a continuous glucose monitor (or serial glucometer readings if there are financial constraints) to track how the patient’s diet is impacting their glucose levels and use that data to formulate a personalized treatment plan.
I hope you found this information useful and helpful in your journey back to a healthier and happier life. If you are someone who is tired of the conventional medical system and wants to get a precision medicine approach to your health care, then schedule a free 15-minute appointment.
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1. Patel N, Taveira TH, Choudhary G, Whitlatch H, Wu WC. Fasting serum C-peptide levels predict cardiovascular and overall death in nondiabetic adults. J Am Heart Assoc. 2012 Dec;1(6):e003152. doi: 10.1161/JAHA.112.003152. Epub 2012 Dec 19. PMID: 23316320; PMCID: PMC3540682.
2. Zeevi D, Korem T, Zmora N, Israeli D, Rothschild D, Weinberger A, Ben-Yacov O, Lador D, Avnit-Sagi T, Lotan-Pompan M, Suez J, Mahdi JA, Matot E, Malka G, Kosower N, Rein M, Zilberman-Schapira G, Dohnalová L, Pevsner-Fischer M, Bikovsky R, Halpern Z, Elinav E, Segal E. Personalized Nutrition by Prediction of Glycemic Responses. Cell. 2015 Nov 19;163(5):1079-1094. doi: 10.1016/j.cell.2015.11.001. PMID: 26590418.