What is a Blood Sugar Meter?

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  • Written By: Helga George
  • Edited By: Michelle Arevalo
  • Last Modified Date: 03 October 2019
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A blood sugar meter is a device for measuring glucose levels in blood, that is used by diabetics to test their blood sugar levels at home. It is also known as a glucose meter. It is especially helpful for people with Type I diabetes in managing their condition.

Originally, glucose levels were tested in urine, but there are several drawbacks to this procedure. In particular, it does not allow the testing of low levels of glucose. Home-use blood sugar meters were developed that use a fingerprick droplet of blood. The skin is pierced with a lancet, and the drop of blood is put on a chemical-coated test strip that has been inserted into the blood sugar meter. The chemicals react with glucose, and the meter displays the glucose reading as a number in millimoles per liter (mmol/l), or milligrams per deciliter (mg/dl).

There are at least 25 types of blood sugar meters commercially available. In the United States, the choice is often dictated by the cost of the test strips. These can vary greatly, and insurance companies often prefer certain brands of meters, due to test strip costs. The brands of blood sugar meter differ in their features, such as whether the data can be downloaded to a computer. The meters, however, cannot always be used with Apple® computers.


One very important factor among different blood sugar meters is whether they display the glucose levels as whole blood, which is what they measure, or as the plasma equivalent. Plasma is a component of blood, and commercial labs test the levels of glucose in plasma, which gives higher readings. Some glucose meters use a conversion factor, and display the equivalent reading for the plasma reading. If this is the case, it is important that one’s doctor be aware that the readings are plasma equivalents when evaluating the patient's record of glucose readings.

Some new blood sugar meters allow testing of alternate sites, such as the forearm or upper arm. There may be problems with this method, however, since the glucose levels in the fingertip change more quickly than in other parts of the body. Therefore, readings from these alternate areas may not be correct, because the glucose levels may be different at various times of day, such as after insulin is taken, or following exercise or a meal.

Blood sugar meter generally displays units as mg/dl in the United States, Japan, France, India, and Israel — while the units are expressed in mmol/l in the United Kingdom, Canada, China, and Australia. Germany uses both methods of measurement. To convert between the two, multiply mmol/l by 18 to get mg/dl; or divide mg/dl by 18 to get mmol/l. Many blood sugar meters are capable of displaying both types of units. It is very important to make sure to use the correct setting for the standard of one’s country.

The most common blood sugar analyses are of fasting blood glucose levels usually taken just after rising for the day. It is not uncommon for diabetics to use a blood sugar meter upon waking, before meals, two hours after eating meals, at bedtime, and then at three AM. A reading of 126 mg/dl (7.1 mmol/l) is generally the cut-off point for a diagnosis of diabetes. Levels between 100-126 mg/dl (5.7-7.1) indicate pre-diabetes — a pre-disposition for developing diabetes. Individuals usually try to keep their blood sugar levels between 80-100 mg/dl (4.5-5.7 mmol/l).

Having blood sugar levels both too high and too low can be dangerous. The condition of having high blood sugar levels is known as hyperglycemia, which generally does not show symptoms until levels are very high. Individuals with persistent glucose levels of 230-270 mg/dl (13-15 mmol/L) after fasting should immediately see a doctor.

In contrast, hypoglycemia is the condition of having excessively low blood sugars. This is often evident from symptoms of shakiness, confusion, and light-headedness, but not everyone experiences these signs. Hypoglycemia is a particular problem for Type 1 diabetics, who must inject insulin. Blood sugar can spike severely downwards after an insulin injection. Monitoring with a blood sugar meter is of particular importance for this class of diabetics, who sometimes test their blood glucose up to 12 times per day.

The use of a home blood sugar meter has proven to be an invaluable tool in helping diabetics manage their condition. This is especially true for Type I diabetics, since they need to inject insulin, and their blood glucose levels can plummet dangerously. Type 2 diabetics are able to track the effects of lifestyle changes, such as diet and exercise, on their glucose levels.


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Post 3

I wouldn't write off the more expensive blood sugar meters just yet, Ruggercat and Cageybird. Meters in general are allowed to be off by as much as 25% in either direction, I think. Yes, a store brand may be cheaper, but if your diabetes control plan includes insulin injections after meals, you're going to want the best and more accurate numbers possible.

A lot of insurance policies do cover many of the the costs of higher-end test strips and meters, so the final cost to you would be comparable to less accurate store brand meters.

Post 2

@Cageybird, that's how they get you when you're first diagnosed and shopping around for the best blood sugar meter. There's always an ad on TV for a free blood sugar meter, but they leave out the part where the test strips cost $100 a box or more. It's like giving away a free cellphone because they can get more money for the service contract. Personally, I think the blood sugar meter thing is a racket. The store brands are nearly as good, and the strips are ten times cheaper.

Post 1

I have found that my store-brand blood glucose monitor is nearly as accurate as my wife's national brand meter. The main difference is the cost of the strips. Her test strips can run over $100 a box, while mine average around $9 for 25 strips. I don't know if I would rely on my blood sugar meter if I were an insulin-dependent diabetic, but it's good enough to get an idea of where my blood sugar level is after a heavy meal or in the morning before breakfast.

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