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What is the Highest Blood Sugar Level That is Safe?

Food that we consume provides energy. Carbohydrates, lipids, and proteins are the main constituents of food. The end products of these complex molecules are glucose, fatty acids, and amino acids respectively. The amount of glucose in our blood determines our health. While a normal blood glucose level is needed for proper functioning, too high levels can cause problems. In this article, we discuss what is the highest blood sugar level that is safe and know the unhealthy range that indicates a problem.

Metabolism of Carbohydrates in the Body

Carbohydrates in the form of complex molecules like starch and disaccharides are converted into simple sugars called monosaccharide. Such monosaccharides found as the end product of digestion are glucose, fructose, and galactose. A part of monosaccharides formed is transported to the liver. Some of them are also used by the brain and muscles directly. A few of them like fructose is sent to the liver for metabolism where they are converted into either glucose or fat.

Glucose is absorbed directly and metabolized to release energy. The parts of the human body like brain, liver, and muscles depend upon glucose for energy. Out of the total glucose found at the end of digestion are either used up by the cells to produce energy or to convert into glycogen or some into fat. The level of glucose is maintained in the body by several metabolic reactions. For example, excess of glucose is converted into glycogen and the reverse reaction occurs when there is demand for glucose or in other terms energy. These are known as anabolic and catabolic reactions respectively. Hence for these reactions to occur, the level of glucose in the blood is very important. When the blood glucose levels are maintained within the normal range, these and other body functions continue properly, or else,

What is the Highest Blood Sugar Level that is Safe?

What is the Highest Blood Sugar Level that is Safe?

There are the standard ranges of glucose level in the blood, which are taken as references to decide the health of an individual. It may also vary slightly in different persons depending upon several factors like age, sex, the kind of work they are performing. It is important to know what is the highest blood sugar level that is safe.

For a healthy individual, the optimum level of blood glucose is calculated in two different situations. The first test is done before meals or when fasting. It should be between 72 to 99 mg/dL or in other words, 4.0 to 5.4 mmol/L. The second value is taken after meals. The test is done after 90 minutes to 120 minutes of taking food. It should be below 140 mg/dL.

For a diabetic patient with type 1 diabetes which is insulin-dependent, the glucose level ranges between 80 and 130 mg/dL in fasting or between 4 and 7 mmol/L before consuming food. After 2 hours of taking food, it may range from 5 to 9 mmol/L or else below 9 mmol/L.

For patients with type 2 diabetes mellitus, at the time of fasting, blood sugar would be between 80 and 130 mg/dL or 4 to 7 mmol/L and after the meals, should be below 180 mg/dL or 10 mmol/L. Anything over and above this is considered unsafe.

The levels that are considered normal can be said safe and healthy for a person. However, beyond the highest blood sugar level that is safe, it can cause medical problems and complications of diabetes. Diabetes management and maintenance of normal blood glucose levels are possible with appropriate treatment, proper diet, and a healthy lifestyle. In addition to that, regular monitoring of blood glucose levels helps.

Studies have shown that regular blood glucose monitoring is a necessary part of diabetes prevention and self-care.1 It also keeps you aware of your blood glucose levels and facilitates the need to have a healthy diet and lifestyle, along with medications, if necessary.

Some of the important blood tests to monitor blood glucose levels include Random Blood Glucose test, fasting blood glucose test, oral glucose tolerance test and HbA1c tests are conducted. These values help to determine the highest blood sugar level that is safe for a person. They also help asses the risk of diabetes and keep a check on the performance of the medications.

  • Random Blood Sugar (RBS): This test is performed at any time hence the name random blood sugar test. It helps to diagnose diabetes. The normal range is below 200 mg/dL or 11.1 mmol/L. The person is suspected to have diabetes if the test value is higher than this value.
  • Fasting Blood Sugar (FBS): This is usually done in the morning because the person would be fasting for 8 hours. Thus, it gets the name Fasting Blood Sugar Test. A person who is at risk of type 2 diabetes may have the range between 100 to 125 mg/dL or 5.5 to 6.9 mmol/L. The people who have this range along with other symptoms of type 2 diabetes are more prone to suffer from diabetes type 2. These people have to take care to prevent the disease. Presence of 126 mg/dL or more glucose shows that the person is diabetic and needs to be treated.
  • HbA1c Test: This test directs a doctor to assess the variation of blood sugar level in 3 months period. The healthy range is 6% or below 42 mmol/mol for normal individuals and above 6.5% or above 48 mmol/mol for diabetic patients. This test suggests that a person is pre-diabetic if the value is between 6 to 6.5% or 42 to 47 mmol/mol.
  • OGTT: This is the abbreviation of the Oral Glucose Tolerance Test. In this method, a blood test is done two times to find out the range of glucose in the blood. First is as usual FBS and second is after 2 hours of intake of having a drink which contains 75g of glucose. In between, the person is advised to take rest after drinking the sweet liquid until the next blood test is over. The values of this test are as follows: 200 mg/dL or above for diabetic patients, below 140 mg/dL for normal individuals and would be between these two values for pre-diabetic people.


It is advisable to know the range of blood sugar and to undergo these tests once in a year, to know the risk of diabetes. Taking care to prevent it is also equally important. Knowing the highest blood sugar level that is safe, helps to plan appropriate treatment and lifestyle measures. The person would be under observation and follow-ups at regular intervals are needed to avoid the complications of diabetes. Hence, the health professionals advice a person to get a thorough body check-up once in a year particularly who are aged 35 years and above. Continuous monitoring is required for a diabetic patient to stay healthy.


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Team PainAssist
Team PainAssist
Written, Edited or Reviewed By: Team PainAssist, Pain Assist Inc. This article does not provide medical advice. See disclaimer
Last Modified On:August 25, 2022

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