Question
How is diabetes diagnosed?
How is diabetes diagnosed?
Answer
Let’s start by talking a little bit about what “non-diabetic” parameters are. If you get blood drawn and lab work done by at your primary care clinic, you will hopefully get a printout (or an online version) of your results and what are considered “usual” values (and hopefully the opportunity to talk to your doctor about them). A “non-diabetic” fasting (nothing to eat for 8-12 hours before the blood test) blood glucose level is 70-99 mg/dL, and if you don’t have any issues with blood glucose regulation, your blood glucose levels won’t budge over that even if you’ve eaten something high in carbohydrate the night before. Over the years I’ve had many patients “deny” that anything was wrong because they “indulged” the night before the lab test; and I’ve had to be the one to point out that if everything was working as usual that the body would be able to regulate the blood sugar levels despite the birthday cake (or whatever) it was that you ate.
If you have an “out of range” fasting blood glucose, your primary care provider might send you for an Oral Glucose Tolerance Test (OGTT) to diagnose pre-diabetes or overt diabetes. Details of this procedure are listed here (http://www.joslin.org/info/diagnosing_impaired_glucose_tolerance_IGT.html). This particular test does involve more time and money so insurance coverage and the person’s ability to go through the test will come into play. If someone is not willing or able to do the OGTT, the primary care provider will likely order additional lab work to try to determine the diagnosis of diabetes. If your fasting blood glucose level is between 100-125 mg/dL, this level is called “pre-diabetes,” which is pretty serious as you have a 25% chance of progressing to diabetes in 3-5 years. At the same time, if someone has two consecutive fasting blood glucose levels of 126 mg/dL or greater, or a random blood glucose level of 200 or greater, that is enough for us to diagnose diabetes.
We can also do a lab test called an Hemoglobin A1c (A1c) to monitor those we suspect are at risk for Type 2 diabetes. I list this one last because when I started my career 20 years ago this lab test was not standardized and could not be used to “diagnose” diabetes. I'm glad that we have this available to us now as having one blood test to help diagnose you is way less time intensive and expensive than taking the glucose drink for an OGTT (although I hear it doesn’t taste as awful as it used to). An A1c is a measure of the average concentration or percentage of glucose “clinging” to the red cells in our blood. Think of it this way—picture your red blood cells as M & M’s and the A1c is a measure of the “thickness” of the candy coating. Some people have called in an “average blood sugar over 3 months” but that really isn’t an accurate description. A “non-diabetic or non-pre-diabetic” A1C is between 4.2-5.8%. If someone’s A1C is over 6.5% that cause to diagnose someone with diabetes. We will then try to keep their A1C less than 6.5-7% unless they are other circumstances at play like advanced age or an advanced chronic condition (e.g. advanced heart disease). (A good “goal” A1c is something that every diabetic should discuss with their doctor).
Some of you might be old enough to remember the term “borderline diabetes;” and you might still hear this thrown around. This was never an actual diagnosis even though it was often used to refer to either pre-diabetes or diet/exercise controlled type 2 diabetes. The main problems with that term was that no one could ever tell you what that really meant (i.e. criteria for diagnosis) or feel that they should take their diabetes seriously as they were not in need of medicine. If you use this term today (and you know who you are), someone (me) will probably remind you that that’s analogous to being “borderline pregnant.” You either are, or you aren’t diabetic .
Let’s start by talking a little bit about what “non-diabetic” parameters are. If you get blood drawn and lab work done by at your primary care clinic, you will hopefully get a printout (or an online version) of your results and what are considered “usual” values (and hopefully the opportunity to talk to your doctor about them). A “non-diabetic” fasting (nothing to eat for 8-12 hours before the blood test) blood glucose level is 70-99 mg/dL, and if you don’t have any issues with blood glucose regulation, your blood glucose levels won’t budge over that even if you’ve eaten something high in carbohydrate the night before. Over the years I’ve had many patients “deny” that anything was wrong because they “indulged” the night before the lab test; and I’ve had to be the one to point out that if everything was working as usual that the body would be able to regulate the blood sugar levels despite the birthday cake (or whatever) it was that you ate.
If you have an “out of range” fasting blood glucose, your primary care provider might send you for an Oral Glucose Tolerance Test (OGTT) to diagnose pre-diabetes or overt diabetes. Details of this procedure are listed here (http://www.joslin.org/info/diagnosing_impaired_glucose_tolerance_IGT.html). This particular test does involve more time and money so insurance coverage and the person’s ability to go through the test will come into play. If someone is not willing or able to do the OGTT, the primary care provider will likely order additional lab work to try to determine the diagnosis of diabetes. If your fasting blood glucose level is between 100-125 mg/dL, this level is called “pre-diabetes,” which is pretty serious as you have a 25% chance of progressing to diabetes in 3-5 years. At the same time, if someone has two consecutive fasting blood glucose levels of 126 mg/dL or greater, or a random blood glucose level of 200 or greater, that is enough for us to diagnose diabetes.
We can also do a lab test called an Hemoglobin A1c (A1c) to monitor those we suspect are at risk for Type 2 diabetes. I list this one last because when I started my career 20 years ago this lab test was not standardized and could not be used to “diagnose” diabetes. I'm glad that we have this available to us now as having one blood test to help diagnose you is way less time intensive and expensive than taking the glucose drink for an OGTT (although I hear it doesn’t taste as awful as it used to). An A1c is a measure of the average concentration or percentage of glucose “clinging” to the red cells in our blood. Think of it this way—picture your red blood cells as M & M’s and the A1c is a measure of the “thickness” of the candy coating. Some people have called in an “average blood sugar over 3 months” but that really isn’t an accurate description. A “non-diabetic or non-pre-diabetic” A1C is between 4.2-5.8%. If someone’s A1C is over 6.5% that cause to diagnose someone with diabetes. We will then try to keep their A1C less than 6.5-7% unless they are other circumstances at play like advanced age or an advanced chronic condition (e.g. advanced heart disease). (A good “goal” A1c is something that every diabetic should discuss with their doctor).
Some of you might be old enough to remember the term “borderline diabetes;” and you might still hear this thrown around. This was never an actual diagnosis even though it was often used to refer to either pre-diabetes or diet/exercise controlled type 2 diabetes. The main problems with that term was that no one could ever tell you what that really meant (i.e. criteria for diagnosis) or feel that they should take their diabetes seriously as they were not in need of medicine. If you use this term today (and you know who you are), someone (me) will probably remind you that that’s analogous to being “borderline pregnant.” You either are, or you aren’t diabetic .
Want to keep reading? Click on the link! http://www.joslin.org/info/all_about_a1c.html
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