Understanding Glucose Levels

Written by Kimberly Holland | Published on January 24, 2012
Medically Reviewed by Peggy Pletcher, RD, CDE on April 15, 2014

What Are Blood Sugar Levels?

When we eat foods that contain carbohydrates, the digestion process turns them into sugars that are released into blood. Those sugars are then transported through the blood and travel to the cells. The pancreas, a small organ in the abdomen, releases a hormone called insulin to meet the sugar at the cell. Insulin will connect onto spots on some cells of the body and act as a “bridge,” allowing the sugar to go from the blood and into the cell. The cell uses sugar for energy, and blood sugar levels go down.

With diabetes, there is either a problem with the cell using insulin, a problem with the pancreas producing insulin, or both.

  • With type 1 diabetes, the body stops making insulin completely.
  • With type 2 diabetes, it is usually a mix of the cells not using insulin well (which is called insulin resistance) and the pancreas not making enough insulin.
  • With prediabetes, it is usually a problem with the cells not using insulin well.

When a person has diabetes, his or her body is not able to get the sugar from the blood into the cells. This causes high levels of blood sugar. This frequently happens after consuming a meal high in carbohydrates.

When to Check Blood Glucose Levels

Talk to you doctor or healthcare providers about the best times to check your blood glucose, as optimal times vary by person.

Some options include:

  • after fasting and/or before meals
  • before and after meals, to see the impact that the meal had on your blood sugar
  • before all meals to decide how much insulin to inject
  • at bedtime
  • when you wake up in the morning

Bring a record of your blood sugar results to doctors’ appointments so you can review it and make changes to your treatment if necessary.

How to Check

A blood sample is required to check blood glucose levels. The most common type of blood glucose monitor requires using a lancet to prick the end of your finger to draw a small drop of blood. This drop is then placed on a disposable testing strip that is inserted into an electronic blood glucose meter. The meter measures the level of glucose in the sample and returns a number on a digital readout.

Some people who have diabetes may use a continuous glucose monitor—a small wire inserted beneath the skin of the abdomen that measures blood glucose levels every five minutes and delivers the results to a monitor device worn on the person’s clothing or in a pocket. This allows the patient and doctor to keep a real-time reading of blood glucose levels.

Recommended Blood Sugar Targets

Blood glucose numbers are measured in milligrams per deciliter (mg/dL).

The American Diabetes Association recommends the following blood glucose targets for people with type 2 diabetes:

Before meals: from 70 to 130 for adults.

Two hours after eating a meal: less than 180 for adults.

The American Association of Clinical Endocrinologists and the International Diabetes Federation recommend glucose levels under 110 for fasting and before meals, and under 140 two hours after starting a meal.

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