Why Is Glucometer Reading High? Here’s Why, and What to Do!

Posted May 8, 2020 by Michael Chamberlain - See Editorial Guidelines
glucometer reading high

Many medical devices are becoming more helpful, more convenient, and easier to use without a doctor’s support.

Through this self-maintenance, a healthy lifestyle has become easier with the development of technology. With diabetes being a serious medical condition in the U.S, the use of a glucometer for measuring blood sugar levels has made living with diabetes a little easier. 

However, since these readings are determined without a doctor’s support, there is plenty of room for misinterpretations.

One common confusion people have is why the glucometer reading is “high” or “Hi.” This article will give a clear understanding of what this means and what you should do.

Why is Glucometer Reading High? When a glucometer reads high or HI, without an actual number, then it means your blood sugar level is highly elevated. Most glucometers will give an accurate blood sugar reading that is below 600 mg/dL, and some others may go up to 750 mg/dL. If your blood sugar is above the max reading for the glucometer, then it will read as “HI.” Patients may need to seek medical attention when their glucometer reads high.

There are a number of reasons why a glucometer reading may be high. Let’s explain further by diving into the types of reasons why this may happen.

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Why is Glucometer Reading High?

Why Is Glucometer Reading High

Most glucometers will only provide an actual reading for blood sugar that is between 20-600 mg/dL. So, if you have a blood sugar above 600 mg/dL, then the glucometer ready may be “HI,” or “extremely high blood glucose.” If it is below 20 mg/dL, then it may say “LO” or “extremely low blood glucose.”

Therefore, the most apparent reason why a glucometer reading is high is because of high blood sugar levels. This means your blood sugar level may be dangerously high. 

This indicates hyperglycemia that may be severe and require medical attention right away.

Unfortunately, when a glucometer reads HI, it does not provide a numerical value. So, patients may not know what exactly their blood sugar level is. This can be worrisome in many instances.

Many glucometer manufacturers haven’t enabled software that would provide numerical values when your blood sugar exceeds a certain amount. So, when a person has dangerously high blood sugar levels, they may not know what exactly they should do without knowing the exact reading. 

Because these readings are in words, they can be interpreted in several ways. One’s blood sugar may be way above or below what they think it is, leading to severe hyperglycemia or hypoglycemia.

Glucometer reading high

Glucometer Machine Errors

Strangely enough, some glucometers can shut down or show an error when there is a mechanical issue or if the glucometer has been exposed to extreme temperatures. At these times, the glucometer would not even show, warn, or alert users of dangerous blood sugar levels.

There may be rare instances where mechanical issues cause the glucometer to read high. Or it may provide you with an inaccurate reading, which could prove to be dangerous.

Other scenarios can cause errors and inaccurate readings on a glucometer. Most of these, though, are user errors. They include having a substance on your finger where you’re getting a blood sample, using a testing site that won’t produce accurate readings, or not applying enough blood to the test strip.

You will also need to make sure you are using the right test strips with the right glucometer to ensure accuracy. Expired test strips may also cause errors with glucometers. So, check the expiration date on your test strips before using them.

Should I Worry if My Glucometer Reading is High?

Why Is Glucometer Reading High

In most cases, when your glucometer reads high, you should be alerted and somewhat concerned, but you should remain calm and collected. 

If your glucometer is reading high and you are experiencing symptoms of hyperglycemia, then you should call your doctor right away. Based on the severity of your symptoms, your doctor will instruct you on what steps you need to take to gain control over your blood sugar levels.

If your blood sugar levels continue to rise, then you are at risk for diabetic ketoacidosis (DKA). This is a life-threatening condition and should be treated immediately.

So, if your glucometer is reading high, then your best option is to recheck your blood sugar to make sure it was not a mistake or error. If the reading is the same, then call your doctor immediately.

Are Glucometer Readings Showing “High” Accurate?

According to the FDA, glucose meter values should be:

  • Within 15% of the results obtained from a lab 95% of the time
  • Within 20% of lab measurements 99% of the time

That is, a glucometer reading of 100 mg/dL can vary as low as 80 mg/dL or high as 120 mg/dL, and then it’s considered accurate. 

To better measure the accuracy of the glucometer, take it with you on your next visit to have a lab glucose test. Then check the blood just after the test and compare the accuracy with the lab test. For the best results, it’s recommended to request the lab to process the test within 30 minutes.

The FDA releases updated recommendations for blood glucose meters. This includes updated guidelines for measuring the accuracy of glucometers.


We hope this has been of use to you in understanding why your glucometer reading is high. If you have any doubts, then always consult a medical practitioner.

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