Get to Know Your Lab Tests: A1C, eGFR, UACR, and More
By Dr. Francine Kaufman
People with diabetes often receive a variety of lab tests to monitor their diabetes management and their risk of complications. Dr. Fran Kaufman breaks down the most common tests, what they measure, and what values you should aim to achieve
For many people with diabetes, getting lab tests is a common occurrence. These tests are used by your healthcare team as a way to measure your health and your diabetes management. It’s good to know what the most common lab tests are for people with diabetes, including their names, what they measure, and why they are ordered. More importantly, you should know your own latest lab results and ask your healthcare professional for a digital or paper copy of the lab slips. Keep a copy of your lab results in a safe place, like a notebook or a drawer, or scan them into your computer. It is your right to have this information.
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Many diabetes lab tests are done at the time of diagnosis and then annually after that. They are used to assess the effectiveness of your diabetes management, to determine if you are at risk for other health challenges (such as high cholesterol levels), or if you are developing diabetes complications (such as kidney problems). The purpose of this article is to introduce you to each of these lab tests, what they measure, and what the American Diabetes Association’s recommended target range is for each of them.
A1C: Hemoglobin A1C (HbA1C, glycated hemoglobin test, glycohemoglobin) is best referred to as A1C. This test can be done with a fingerstick and reported within minutes in your healthcare professional's office, or it can be done in a laboratory through a venipuncture (a needle placed in the vein to withdraw blood) and reported within a few days. An A1C test gives you an estimate of your average blood sugar level over the past two to three months by measuring how much glucose is attached to your red blood cells. Red blood cells survive in your body for two to three months; if your blood sugar levels have been high, more glucose sticks to your red blood cells. For people with type 1 diabetes, A1C is usually measured every three months. For those with type 2 diabetes, if the A1C is at target, it can be measured every six months; if there is a change in diabetes treatment or if your A1C increases, your healthcare team may change this to every three months. The A1C test can also be used to help diagnose diabetes, and a person’s A1C value also determines their risk of developing diabetes complications.
The goal for a person’s A1C, according to the American Diabetes Association, is less than 7% in adults and 7.5% in children. However, A1C targets should be individualized, taking into account older age, other significant medical conditions, and the risk for severe hypoglycemia. Of note, the A1C level can be influenced by anemia (low blood cell count), chronic kidney disease, abnormalities of the hemoglobin molecule (sickle cell disease, thalassemia), and recent blood transfusion. You should know your A1C and actively work to be at your target or on your way there.
Since an A1C reflects average blood glucose over the last few months, it cannot provide information about day-to-day diabetes management. Many people with diabetes and their healthcare teams have turned to time in range (TIR) as an additional measure of diabetes management. TIR is the percentage of time that a person spends with their blood glucose levels in their target range; the most common target is between 70-180 mg/dl. TIR captures daily variations in blood glucose levels, and provides a powerful tool for people with diabetes to see and understand patterns in blood glucose throughout the day. As telemedicine has become more common during the COVID-19 pandemic, TIR has helped healthcare teams understand a person’s diabetes management when they can’t visit in-person or get lab tests. Read more about time in range here.
Blood Lipid Levels: Lipids are fatty substances found in the blood. The blood lipids test measures total cholesterol, LDL-cholesterol (low-density or “bad” cholesterol), HDL-cholesterol (high- density or “good” cholesterol), and triglycerides (another form of lipids that can be harmful at high levels). The lipids that are measured when you have a cholesterol test or a lipid panel are those that are being carried in the blood by proteins called lipoproteins.
We all need to have cholesterol in our bodies because cholesterol is a critical component of the membranes (the outer coverings) of our cells.
LDL-cholesterol is considered bad because it builds up in blood vessels and can obstruct or block blood flow, putting someone at risk for heart complications.
HDL-cholesterol is good because it helps clear excess LDL from the blood.
High triglycerides can contribute to thickening of the walls of arteries and therefore to heart disease, and very, very high triglyceride levels can contribute to inflammation (the body’s way of fighting infection – too much inflammation over time can cause health issues).
Your healthcare professional might give you a ratio of total cholesterol-to-HDL cholesterol. This is done by dividing the total cholesterol value by the HDL value. If the total cholesterol is high because of elevated good HDL-cholesterol, this ratio corrects for that and shows a lower risk of heart disease.
Blood lipids should be measured when you are diagnosed with diabetes and every year after in adults (there are different recommendations for children). If you have heart disease (and need to assess response to lipid-lowering treatments), they should be measured more often. The recommended values for blood lipids are:
LDL cholesterol: less than 100 mg/dl
Triglycerides: less than 150 mg/dl
HDL-cholesterol: greater than 40 mg/dl in men and 50 mg/dL in women
Overall non-HDL-cholesterol: less than 130 mg/dl
There isn’t a value given for total cholesterol because the American Diabetes Association focuses much more on the other lipid levels than the total amount of cholesterol, and mostly on the bad LDL-cholesterol and non-HDL-cholesterol levels.
Liver Function Tests: A blood test is used to measure the two liver enzymes (or bodily chemicals), ALT (alanine transaminase) and AST (aspartate transaminase), at diagnosis and yearly. ALT is an enzyme that helps convert proteins to energy for the liver cells. AST is an enzyme that helps break down amino acid nutrients. When the liver is damaged, ALT and AST leak into the bloodstream, raising how much of each enzyme is found in the blood. Often ALT and AST are part of a set of comprehensive metabolic tests that measure many compounds in the blood as a general health screen, as a follow up to a medical condition, or to assess the body’s response to medications that could affect the liver. In people with type 2 diabetes, ALT and AST may be helpful in trying to assess whether fatty liver tissue is present.
The normal ranges for these liver enzymes vary by laboratory. If you get ALT and AST measured, ask for the lab sheet report so that you can check if your values fall in the “normal” range.
Urine albumin-to-creatinine ratio (UACR): This test for elevated albumin protein in the urine can indicate early kidney disease. Without kidney damage, very little protein is found in the urine; kidney damage from diabetes (or other causes) causes albumin to increase in the urine. Learn more about kidney disease and UACR here.
The spot test for UACR can be done at any time: the calculation compares how much albumin is in the urine to how much creatinine is in the urine. Creatinine is the waste product in urine that comes from the normal, day-to-day wear and tear of our muscles. To specifically get the UACR measurement, the laboratory divides the albumin concentration by the creatinine concentration.
Normally, the UACR is less than 30 mg/g.
A UACR of 30 to 300 mg/g refers to albumin above the normal range but below the level of detection of other tests for total protein in the urine.
A UACR greater than 300 mg/g is severely elevated.
Urinary ACR is a truly important screening test that is done at the time of diagnosis and then usually at yearly intervals. Sometimes UACR can appear high even if you don’t have kidney damage (due to anything that increases albumin excretion in the urine, such as a urinary infection or menstruation), so if the UACR is elevated, the test should be repeated. A 24-hour urine collection should be considered before kidney disease is diagnosed.
Blood Creatinine and eGFR: The blood creatinine level indicates how well the kidneys are working. Creatinine is a waste product made by the body through normal breakdown and metabolism of our muscles. Creatinine is normally excreted in the urine and cleared from the blood unless the kidneys are not functioning fully – in that case, creatinine levels will increase in the blood.
The normal range for creatinine in the blood is 0.84 mg/dL to 1.21 mg/dL, although these normal values vary between men and women (men have higher levels because they have higher muscle mass), by age (blood creatinine levels are higher in older people), and from lab to lab. Blood creatinine can also increase from dehydration, certain medications (including the dietary supplement creatine), and in those who eat lots of meat. If the blood creatinine level is high, and still high after the test is repeated, your healthcare professional will look for kidney damage – which could be reversed, halted, or slowed if caught early.
The eGFR stands for the estimated glomerular filtration rate and is another important test to measure your kidney function. It is calculated from your blood creatinine, your age, body size, and gender. In addition, race has been used to also estimate GFR; however, this is controversial since race is not a biologic construct, and there is no accounting for the tremendous diversity within communities of color.
If your eGFR is low, your kidneys may not be working fully. The normal eGFR value is greater than 90 mL/min/1.73 m2. An eGFR below 60 mL/min/1.73 m2 can indicate chronic kidney disease. eGFR values are only reported for adults.
Additional Lab Tests:
Thyroid Function Test: People with type 1 diabetes and people with type 2 diabetes with signs of thyroid gland dysfunction should have their TSH (thyroid stimulating hormone) value measured. The normal range is 0.4 to 4.0 mU/L. TSH levels increase when the thyroid gland is not producing enough thyroid hormone due to primary thyroid disease (hypothyroidism), and decrease when the gland is over producing thyroid hormone (hyperthyroidism). Both hypothyroidism and hyperthyroidism are most commonly caused by autoimmune disorders, in which your body’s immune system attacks the thyroid gland. Since type 1 diabetes is an autoimmune disorder, people with type 1 need to be screened for other autoimmune processes, like autoimmune thyroid disorders.
Celiac Screen: In people with type 1 diabetes, celiac disease should be screened with a test that detects an antibody to gluten, called tissue transglutaminase IgA antibody. Celiac disease occurs when the body perceives gluten (a type of protein found in wheat, rye, and barley) as a threat to health and makes an antibody molecule to protect against it. If the screening test for celiac is positive and antibodies to gluten are found, a full celiac lab evaluation is necessary to look for other antibodies directed against gluten. In addition, labs can determine if someone has the common genes associated with celiac disease. If celiac disease is diagnosed, it is treated by eliminating all gluten from the diet.
This is a quick synopsis of the common lab tests done in people with diabetes. It’s helpful to know what your healthcare professional is checking for when a blood test is ordered, and it’s important to know and keep track of the results. If you have questions about why a certain test was ordered – or not ordered, now that you know the American Diabetes Association recommendations – ask your healthcare team. With more knowledge about your own diabetes management and how it relates to your lab results, you’ll be better able to optimize your health and your diabetes outcomes.