The hemoglobin A1C was introduced as a means for monitoring the "control of glucose metabolism" in the late '70s, and quickly became the gold standard, giving us a three-month average of where blood glucose levels stand. However, an average blood glucose can be deceiving, because it doesn’t take into consideration the highs and lows that may be occurring between tests.
What Is GlycoMark?
The GlycoMark test is based on a molecule called 1,5-AG (short for 1,5-anhydroglucitol), discovered in 1880. Researchers noticed that diabetic patients have less 1,5-AG in their blood, and it drops even lower when their blood sugars are running really high.
The 1,5-AG was an independent predictor of postprandial hyperglycemia and was more sensitive and specific than the A1C. 1,5-AG reflects glucose extremes, usually detecting the after-meal glucose levels, while A1C reflects your glucose average overall, and is less sensitive to your glucose ‘excursions,’ or times when your glucose goes to extremes (usually after a meal).
The frequency of glucose excursions is directly related to the risk of complications or even death with Diabetes.
Typically, there are a couple ways to check if you are having a glucose excursion:
- Check your glucose before your first bite of a meal, and also 2 hours later. How high does your glucose get after a meal? This could be an excursion.
- Use a continuous glucose monitor (CGM), to keep track of your glucose- you can check glucose at any time (every hour, if you wanted, and with no finger poke). This can provide some insights into control with their standard deviation and variance calculations. These numbers will tell you how controlled you are.
Since most people don’t check their after-meal glucose frequently enough to know if they are having an excursion, and the CGM is tough to get covered by insurance, knowing how controlled you are is often a guessing game.
Why It Helps:
That’s why the 1,5-AG may be useful to compliment the A1C test… but not to replace it. Especially for patients that have normal or moderate control of their A1C, it is tough to detect when glucose levels are stable and consistent throughout the day, or if they vary widely with multiple excursions.
In fact, it’s possible to have a completely normal A1c and still have extreme high and extreme low blood sugar levels. These extremes can be even more dangerous.- Nina Ghamrawi, MS, RD, CDE
It is the only FDA-cleared blood test specific to detecting recent hyperglycemia and hypoglycemic excursions. It helps you see recent trends, and understand if your control is getting better or worse. When the Glycomark is used with the A1C, it provides a more complete view of glucose control and can identify people that may benefit from more frequent monitoring, or a diet or medication change.
“In this case, when you don’t have a CGM, Glycomark, along with the A1C, is a very useful tool to know not just your average glucose, but also how stable you are from day-to-day.”- Carolyn McCorkindale, MS, RD, CDE
Lots of mainstream labs now offer the GlycoMark test, including Quest, LabCorp, and Specialty Laboratories, however not all insurances will cover it, since it is not considered a standard test.
Warnings to Keep In Mind
- The test won't work for people with stage 4-5 kidney disease.
- 1,5-AG reflects glucose elevations within a few days, so you’d need to check it more often if you are trying to gain control and reduce excursions.
- The A1C test checks the average glucose in the last 3 months, so you should compare your Glycomark results to oyur A1C to see the whole picture.
- A higher GlycoMark number is better, with a reading above 10 indicating fewer glycemic excursions.
How Do I Interpret My Results?
Here’s a chart from Glycomark that shows you how to read your results, and how to compare them to your A1C.
it’s possible to have a completely normal A1c and still have extreme highs and lows in your glucose. This is not only dangerous, but really tough to detect without the right tools and without checking your glucose often. That’s why the Glycomark (1,5-AG) test may be more useful together with the A1C test. Especially for patients that have normal or moderate control of their A1C, it is tough to detect when glucose levels are stable and consistent or rise and fall with extremes. If you don’t have a CGM, and you don’t check your glucose after meals, talk with your doctor about getting a 1,5-AG. If you do check glucose after meals, or you have a CGM, discuss the results with your dietitian or Diabetes Educator. They’ll help you make sense of the results and fine-tune your routine.