As people with type 1 diabetes, we are constantly being “tested.” Our hour-by-hour blood sugar levels are under the most scrutiny, but many other aspects of our health fall under the microscope, too.

There are several routine medical tests that people with diabetes are supposed to get regularly, and while they are important, the results are not always as simple as we’ve been led to believe.

Even if you’ve been getting these tests for years, there’s a lot you may not know about them.

We decided to take a closer look at the five most routine lab tests used to assess the overall health of people with diabetes, with our insider expert, Aimee Jose, RN, and DCES (Diabetes Care and Education Specialist), who works with Steady Health in San Francisco.

“Lab results are one of the most challenging things to discuss with patients because there’s so much variability from lab to lab,” explains Jose. “There’s also a lot of controversy within the medical field on how to interpret labs. We’re always learning, so it feels like one day they say to stay away from coffee, and the next day it’s fine to have coffee.”

Jose helps us dive into what these five tests really measure, and what your results actually mean.

Aimee Jose. Image via Steady Health

What is it? The HbA1c (or “A1C”) test officially measures the amount of glucose that has attached to your red blood cells over the course of the prior 3 months. But Jose says the results actually reflect your glucose levels over the past 4 months.

The American Diabetes Association recommends achieving and maintaining an A1C at or below 7.0 percent.

Although it’s generally considered the Gold Standard of diabetes care, “an A1C is not a great indicator of a patient’s overall blood sugar management,” says Jose.

Once touted as the ultimate depiction of diabetes health, the A1C is quickly losing clout as experts turn more to “time in range” as a better indicator of diabetes outcomes.

It’s all about your red blood cells, which change constantly.

While we’re often led to believe that the A1C is a straightforward measure of our average blood sugar level from the prior 3 months, it’s far more complicated than that.

In reality, 50 percent of your A1C result is derived from the most recent month before the test, explains Jose. Twenty-five percent is from the month before that, and 25 percent is from the two months before that.

“It’s a moving target,” explains Jose. “It’s just an estimate and it’s constantly changing. The rate at which people turn over red blood cells is slightly different in every body.”

For instance, a pregnant woman has a very high red blood cell “turnover rate,” meaning she could have a very low A1C result because most of her blood contains new red blood cells, explains Jose. These cells haven’t been in your bloodstream long enough to have glucose actually attach to them.

“If you just donated blood, you just got rid of old and new red blood cells, which means your body is going to replenish your blood supply. There’s far less glucose attached to those new blood cells.”

But wait, it gets even more complex.

The A1C test only measures a tiny percentage of your blood.

Jose explains the science behind that: “Ninety-eight percent of hemoglobin in the red blood cell is hemoglobin A, and 7 percent of Hemoglobin A consists of a type of hemoglobin called HbA1. This is what combines with glucose in a process called glycosylation. Once glycosylation occurs it can not be reversed. HbA1 is made of three parts: A1a, A1b, A1c. A1c most strongly combines with glucose. Only 20 percent of A1a and A1b are glycosylated.”

She says the A1C test can still be useful to look at the bigger picture. For instance, an A1C over 10 or 11 percent is a valuable red flag that could signify other health issues or life-threatening behaviors like skipping insulin doses.

“An A1C of 9 versus 8, on the other hand, doesn’t tell you enough. Or with an A1C of 6.5 versus 7.0, again, there are just too many variables affecting that number.”

What’s a more accurate way to assess overall blood sugar management so you can make necessary changes in insulin doses, nutrition, etc.?

Time in range, measured by using a continuous glucose monitor, is the best tool we have to look carefully at blood sugar management,” says Jose. “The A1C test is simply not an accurate reflection of a person’s overall blood sugar levels.”

But the A1C remains a staple for most physicians, so don’t be surprised if your doctor still insists that you have this test done regularly.

What is it? Your “total lipid profile” measures your LDL (“bad”) cholesterol, your HDL (“good”) cholesterol, your triglycerides (presence of fat in your blood), and your total cholesterol. You can learn about goal measurements for each of these lipid tests here.

Is fasting really necessary for these tests?

“Yes and no,” says Jose. “To get a total lipid panel that includes LDL, HDL, triglycerides, and total cholesterol, you do need to be fasting. However, If you’re just measuring total cholesterol or total HDL, you do not need to be fasting.”

Your LDL and triglyceride tests, on the other hand, do require fasting because the fat in the meal you just ate has not fully cleared from your system. Eating within the recommended fasting window of 12 hours before these two tests could lead to false high measurements.

How to fast safely if you have diabetes

“[Fasting] can be safe, but there are several things to consider and understand before you start skipping meals for the sake of your blood tests,” cautions Jose.

  • How long are you fasting for?
  • What medications are you taking?
  • How do those medications work?
  • Can you maintain safe blood sugars between 70 to 180 mg/dL while fasting without intervening?
  • What is your overall level of diabetes education and control?
  • NOTE: Treating low blood sugars with pure carbohydrates during your fasting window should not throw off your lipid results. Make sure you’re not consuming anything containing fat.

“The most important thing is that you need to understand how your medications work,” says Jose. “Too many people pop pills and take (supplements) because their doctor said they should take it, and they do not learn the mechanisms of action and how to be safe around things like insulin or other diabetes medications that can cause low blood sugar.”

“If you’re not eating, you should not take the fast-acting insulin that covers your meals,” adds Jose. “If you wake up with high blood sugar, you can take a small amount of insulin to correct, but it’s a reduction of the dose you’d normally take.”

Some people with type 1 diabetes actually see blood sugar levels rise due to fasting, which is likely from your liver excreting glucose to provide you with fuel (you know, because you skipped breakfast). In this case, you could take a small bolus when you see your blood sugar starting to rise just as you would to correct an already high blood sugar level.

If you are not comfortable fasting for a blood test, talk to your healthcare team about ways around this.

Should everyone with diabetes be taking a statin to improve cholesterol?

Statins are a pharmaceutical medication that lowers your LDL cholesterol levels by reducing your liver’s natural production of cholesterol. But they continue to be controversial, with research pointing to both their benefits and their risks.

Many cardiologists strongly support the idea that whether or not you have diabetes, anyone between the ages of 40 to 75 years old should be taking a statin. This is also supported by the American Diabetes Association (ADA). Others feel that anyone with diabetes — type 1 or type 2 — in that same age range should be taking a statin. And then many feel statins may be toxic and actually increase insulin resistance and overall risk of developing type 2 diabetes.

“Statins work to lower your risk of a cardiac event — like a heart attack or stroke — beyond just lowering your LDL levels,” explains Jose, who works with an endocrinologist who supports the use of statin therapy in all adults ages 40 to 75 years old.

While making changes in your nutrition and exercise habits can help, Jose points out that lifestyle changes alone can only lower cholesterol levels by anywhere from 5 to 20 percent, depending on the patient.

Additionally, Jose says the cholesterol you eat only accounts for up to 15 or 20 percent of the cholesterol in your bloodstream. Eighty percent of your body’s cholesterol is produced by your liver.

Should you jump on that statin bandwagon? For many, statins bring side effects of intolerable muscle aches and tiredness. For others, a statin may very well be what prevents a future heart attack and prolongs your life.

Myalgia (muscle aches) is the most common side effect of statin use, with documented rates from 1 to 10 percent. Of course, you should consult your doctor if you believe your medication is causing side effects.

What is it? Your blood pressure measures a combination of how much blood is passing through your blood vessels along with how much resistance occurs when your heart is pumping that blood. The narrower your arteries are due to things like smoking, obesity, lack of exercise, poor diet, and genetics, the higher your blood pressure levels will be.

Blood pressure levels of 140/90 or higher should be addressed ASAP.

When blood pressure levels are high for months or years on end without intervention, it can lead to life-threatening conditions like heart disease, and greatly increase your risk of a stroke or heart attack.

Can too much coffee cause false high blood pressure readings?

“It shouldn’t,” says Jose. “Coffee is fine in moderation — like everything else. For most people, 3 to 4 cups per day should not raise your blood pressure.”

Keep in mind that everyone has a different tolerance for caffeine. For some, more than one cup of coffee per day can leave them jittery and racing for hours. For others, 4 cups of coffee are no big deal.

Also, keep in mind that the caffeine in coffee — even without cream and sugar — can raise your blood sugar. Again, for some, it’s about the quantity of caffeine versus just whether or not they should be consuming any at all.

What about blood pressure medications?

One of the most common blood pressure medications prescribed is “beta-blockers,” but there are multiple others too. Most work well with relatively mild side effects, but Jose says it really depends on the patient.

“Is it worth it or not worth it to you as an individual to take a blood pressure-lowering agent?” asks Jose.

For some, making lifestyle changes (like exercising more, losing weight, and quitting smoking) is a feasible and worthwhile approach to improving their blood pressure.

Others may not be willing or able to make impactful lifestyle changes, which means taking a blood pressure-lowering agent is the most logical approach.

“I try to work with every patient as an individual, giving them options,” says Jose. “It’s a constant negotiation — if you’re not going to change a certain habit, then maybe you’re willing to take medication.”

One recent research finding suggests that it’s best to take your blood pressure at night rather than in the morning.

“It’s proven to be more effective at improving blood pressure levels and reducing your cardiovascular risk,” Jose explains.

Note that taking blood pressure medication can also help to preserve kidney function, which can be especially important because poorly controlled diabetes can also put a strain on the kidneys.

Can your blood sugar affect your blood pressure?

The answer is “yes” and “no.”

Short-term: No, a high blood sugar level during a routine blood pressure test should not affect your blood pressure at that time.

Long-term: Yes, in three different ways, according to research published by the Journal of the American College of Cardiology.

  • The blood vessels throughout your entire body incur ongoing damage from persistent high blood sugar levels. Over time, they will lose their ability to stretch, which creates more pressure.
  • Persistent high blood sugars also result in more fluid retention and long-term damage to your kidneys, which increases pressure on your overall circulatory system.
  • Lastly, increasing insulin resistance has been theorized to also increase blood pressure levels. The cause and effect, however, is unclear, since insulin resistance can also coincide with weight gain, a poor diet, and lack of physical activity, all of which can lead to increased blood pressure levels.

As with nearly everything else, the best you can do to improve your blood pressure level is to make basic lifestyle changes in your diet, exercise, and consumption of alcohol and nicotine.

What is it? A microalbumin test uses your urine to measure how well your kidneys are doing their job of filtering waste from your system. Albumin is a protein that is normally present in your blood but should not be present in your urine in large quantities.

Measurable levels of albumin in your urine indicate early signs of kidney disease. Any measurement greater than 30 mg is cause for concern and should be addressed immediately.

Damage to your kidneys can occur quickly and unnoticeably.

Changes in your kidneys can happen very early,” says Jose. “This is why it’s so important to have microalbumin testing done annually, and then treat signs of kidney disease aggressively.”

Unmanaged diabetes, says Jose, is the most common cause of kidney failure in the world. And like they say at the Behavioral Diabetes Institute, “Well-managed diabetes is the No. 1 cause of nothing.”

“We need to protect our kidneys. The kidneys are our body’s filtering system. And those tiny vessels throughout your kidneys are so tender and so sensitive. If we overwork them by forcing them to filter out more and more sugar, those delicate vessels are going to become damaged from overuse.”

High blood pressure levels also damage these blood vessels.

“The pressure in the kidneys is also what’s so destructive,” Jose says. “The force pushing against the vessels. This means high blood pressure levels further deteriorate the vessel lining in your kidneys.”

This means, of course, it’s very important to protect your kidneys by addressing high blood pressure levels.

What if you take diabetes drugs that filter sugar through your urine on purpose?

“With drugs like Invokana and Jardiance — known as SGLT2 inhibitors — they filter excess sugar from your bloodstream by lowering the renal threshold. This means that when your kidneys would normally filter sugar if your blood sugar is over 180 mg/dL, they will start filtering when your blood sugar is as low as 140 to 160 mg/dL,” explains Jose.

Yes, this does overwork your kidneys. It also increases your risk of yeast infections because the excess glucose in your urine can feed the growth of yeast.

“If you’re taking any of these medications that filter glucose out through your urine, it’s very important to have annual labs done on your kidney function through a microalbumin test,” Jose says.

What is it? A dilated eye exam is conducted by an ophthalmologist and takes images of the optic nerve, retina, and blood vessels — all of which can be easily damaged by high blood sugar levels.

Diabetic eye disease (retinopathy) can develop “overnight.”

If you haven’t heard it enough already, Jose is going to say it again: “It’s super important to get your eye exam done every year by an ophthalmologist. You need to have eye exams done to assess your baseline eye health.”

Diabetic eye disease comes with nearly no symptoms and it can develop seemingly overnight. And long-term high blood sugar levels can leave a big mark on your eyes.

Your vision can fluctuate with blood sugar fluctuations.

“Your actual vision changes and fluctuates with your glycemic control,” explains Jose. “If your blood sugars are high, the volume inside your vessels also increases, and then those vessels expand. This puts pressure on the lens and changes your vision.“

As your blood sugar comes down, your blood vessels will relax and your vision will come back to your normal, adds Jose.

“Do not get a new prescription for glasses or contact lenses if your blood sugars have been running high. The actual prescription eye exams from an optometrist should hold-off until your blood sugars are in your goal range again.”

Ask your ophthalmologist to show you your exam images.

“There is so much detail in the images of behind your eyes from the dilated eye exam,” says Jose.

“You can actually see that occluded blood vessel and how it’s starting to splinter off. You can see what your high blood sugars are doing.”

Jose reminds us that diabetic retinopathy is the leading cause of “new-onset blindness” in people ages 20 to 74 years old.

“The damage can happen so quickly due to mild or major changes in your diabetes health, and during pregnancy. Get that dilated eye exam done every year!”


Ginger Vieira is a type 1 diabetes advocate and writer, also living with celiac disease and fibromyalgia. She is the author of “Pregnancy with Type 1 Diabetes,” “Dealing with Diabetes Burnout,” and several other diabetes books found on Amazon. She also holds certifications in coaching, personal training, and yoga.