Understanding lab results when you have diabetes

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Julie Cunningham, MPH, RDN, CDCES, IBCLC

There's a lot to learn when diagnosed with diabetes besides how to manage your day-to-day blood sugar. Before you were diagnosed, you may not have given much thought to lab testing or the importance of understanding lab results. However, now that you've been diagnosed, you're probably wondering, "What do all these tests mean, and how can I use my results to make better decisions about my healthcare?"

Looking at all of the data can be more than confusing. You're not alone in feeling that way! Combined with other areas of your diabetes management, these tests help paint an accurate picture of your diabetes health and overall well-being.

Here's what to know about diabetes lab tests and the results they produce.

Blood lipid panels

Because people with diabetes are at a higher risk for heart disease, it's important to keep an eye on blood lipid levels. Blood lipids are more commonly referred to as cholesterol levels, and they affect cardiovascular (heart) health. If you're living with diabetes, your blood lipids should be checked annually, or more often if your healthcare provider feels it's necessary.

Once you get your test results, here's what each of them means for you:

  • Cholesterol is a waxy substance that helps form a barrier on the outside of your cells. Some cholesterol is necessary, but too much puts your heart at risk. A total cholesterol level under 200 milligrams per deciliter is considered acceptable.
  • LDL (low-density lipoprotein) is often referred to as "bad" cholesterol because it tends to form plaque on the interior walls of our blood vessels. This plaque takes up space and impedes blood flow. Ideally, your LDL will be under 100 milligrams per deciliter.
  • HDL (high-density lipoprotein) is frequently called "good" cholesterol. Imagine HDL as the sanitation crew of your blood vessels: HDL helps reduce plaque buildup in the blood vessels and pulls it back to the liver, where it can be packaged for disposal. Women tend to have higher HDL levels than men because of the benefits of the female hormone, estrogen. The recommendations are that men keep their HDL levels above 40 milligrams per deciliter, and women keep their HDL levels above 50 milligrams per deciliter.
  • Triglycerides are fats that circulate in your bloodstream. Triglycerides can serve as immediate fuel, or they can be stored as fat. When your energy is running low, fat cells release stored triglycerides back into the bloodstream to be used for energy. Your triglyceride level should be less than 150 milligrams per deciliter.

The C-peptide test

The C-peptide test helps determine whether your pancreas is making insulin on its own. When your pancreas releases insulin into the bloodstream, it also releases C-peptide in equal amounts. So, the amount of C-peptide in your blood will tell you how much natural insulin your body makes, if any.

A C-peptide test can be useful in either of these situations:

  • Sometimes it's hard to tell whether a person has type 1 diabetes (and makes little to no insulin on their own) or type 2 diabetes (where their body makes plenty of insulin but can't use it.)
  • Some people with type 2 diabetes stop making insulin after they've had diabetes for several years. A C-peptide test will help determine whether it's time to start using insulin injections or whether oral medications (pills) are still useful.

A normal C-peptide test result is 0.5 to 2.7 nanograms per milliliter. A low C-peptide level may indicate that your pancreas isn't making insulin. A high C-peptide level may mean that you're using large amounts of medications that push your pancreas to produce insulin, such as sulfonylureas (for example, glipizide or glimepiride).

Understanding lab results for thyroid tests with diabetes

About 13% of people with diabetes have thyroid disease, and more than one-third of women with type 1 diabetes are affected by thyroid disorders. A "thyroid panel" is actually a few different tests, although your healthcare provider may start with just a TSH exam and then get additional tests if needed.

  • TSH (Thyroid-stimulating hormone) is made by the pituitary gland near your brain. It signals the thyroid gland in your throat to release T3 and T4. The normal TSH range for an adult is 0.40 to 4.50 milli-international units per liter of blood.
  • T3 (Triiodothyronine) is the active form of thyroid hormone. The normal T3 range for an adult is 100 to 200 nanograms per deciliter of blood.
  • T4 (Thyroxine) is a relatively inactive form of thyroid hormone. It's activated in your liver and other tissues. The normal T4 range for an adult is 5.0 to 11.0 micrograms per deciliter of blood.

Hyperthyroidism (too much thyroid hormone) speeds up your metabolism and may cause rapid heartbeat, sweating, weight loss, bulging eyes, or anxiety. Hypothyroidism (not enough thyroid hormone) slows down your metabolism. You might gain weight, feel tired or cold, or have dry, itchy skin.

How often do I need new lab tests if I have diabetes?

Blood lipids, C-peptide, and thyroid function tests are usually drawn annually if your diabetes is well-managed. A1C is typically drawn every six to 12 months, and blood pressure is monitored at each visit to a healthcare provider. If your healthcare provider changes your medications or finds a lab result that needs further evaluation, they might ask you to get labs drawn more often.

If you feel overwhelmed by the numerous tests on your lab report, the American Diabetes Association encourages people with diabetes to focus on three key measures, known as the "ABCs" of diabetes: A1C, blood pressure, and cholesterol. Understanding your lab results is essential to partnering with your healthcare provider to work toward the best possible outcome: a healthy life with diabetes.

A continuous glucose monitor and/or insulin pump may help you manage your diabetes. Learn more about using these devices on the Edgepark Health Insights blog.

Julie Cunningham, MPH, RDN, CDCES, IBCLC

Julie Cunningham is a Registered Dietitian Nutritionist and a Certified Diabetes Care and Education Specialist. Julie provides online nutrition programs for people who want to end their struggle with diabetes. She can be found at juliecunninghamrd.com and at TameType2.

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