Diabetes mellitus: Clinical

In diabetes mellitus, the body has trouble moving glucose from your blood into the cells – so blood sugar levels are constantly high. Insulin stimulates the movement of glucose into the cells, and glucagon stimulates the movement of glucose into the blood. In type I diabetes the blood glucose stays high because of an autoimmune destruction of the pancreas, which leads to low insulin levels. In type II diabetes, the body makes insulin, but the cells are insulin resistant - meaning they don’t “respond” to insulin by taking glucose in.

Cells’ inability to use insulin translates in classical symptoms of diabetes like polyuria – individuals pee a lot -, polydipsia – they drink a lot of water -, sometimes polyphagia – they eat a lot – and unexplained weight loss. Both type I and type II diabetes get these symptoms – however, with type I, the onset is usually abrupt and usually affects people under 30. With type II, the symptoms gradually worsen over a few months, and individuals usually have risk factors like being over 45 years old, having a first degree relative with type II diabetes mellitus, a body mass index (BMI) over 25, a sedentary lifestyle, or cardiovascular disease, like hypertension.

Now, type II diabetes accounts for about 90% of the diabetes cases, so let’s start there. Diagnosing type II diabetes relies on determining blood sugar levels using one of four tests. The first, and most common test, is a fasting glucose test and it’s where the person doesn’t eat or drink anything except water for 8 hours. Levels of 100 milligrams per deciliter to 125 milligrams per deciliter indicates prediabetes and a level of 126 milligrams per deciliter or higher indicates diabetes. Usually this test is done twice, and two results over 126 milligrams per deciliter are sufficient to diagnose a person with diabetes. Second, we have the oral glucose tolerance test, and it’s where a person is given 75 grams of glucose, and then blood samples are taken at time intervals to figure out how well it’s being cleared from the blood. At the time interval of 2 hours later, a level of 140 milligrams per deciliter to 199 milligrams per deciliter indicates prediabetes, and a level of 200 or above indicates diabetes. However, these two tests have one shortcoming - they only show what’s happening to blood glucose levels in that particular moment in time, so we have no idea how long blood sugar levels have been high. This is where our third test comes in - the HbA1c, which is the proportion of glycated hemoglobin in the blood. When blood glucose levels stay high for too long, glucose begins to stick to proteins that are floating around in the blood or in cells - like hemoglobin. HbA1c levels of 5.7% to 6.4% indicate prediabetes, and 6.5% or higher indicates diabetes. Since red blood cells - and hemoglobin - typically hang around in the blood for up to 4 months, this test reflects blood glucose levels over the past few months. Finally, there’s our fourth test, called a non-fasting or random glucose test, which can be done at any time. A red flag for diabetes is when this test shows a blood glucose level of 200 milligrams per deciliter or higher in an individual that has classic symptoms, like polyuria or polydipsia; or a hyperglycemic crisis.