If you're seeing this message, it means we're having trouble loading external resources on our website.

If you're behind a web filter, please make sure that the domains *.kastatic.org and *.kasandbox.org are unblocked.

Main content
Current time:0:00Total duration:8:23

Video transcript

let's discuss the presentation and diagnosis of diabetes mellitus recall that diabetes mellitus is a group of disorders that can be caused by multiple different underlying mechanisms however all the different types are diagnosed in the same way and that is a combination of clinical presentation and diagnostic tests so let's erase this here and start with the presentation of diabetes mellitus recall there are two types of diabetes type 1 and type 2 and depending on the type the disease presentation will differ and there are three main ways in which someone with diabetes will present before they're diagnosed with disease and they are acute subacute and asymptomatic now let's start with the acute presentation this is the most severe presenting situation and can be life-threatening for both type 1 and type 2 diabetes this individual becomes very sick over a relatively short period of time usually only a couple of days now symptoms will include things like nausea vomiting and abdominal pain and this often results in severe dehydration and as such the individual may even become confused or unconscious as a result in type 1 diabetes this is known as diabetic ketoacidosis or DKA for short and it is how about 30% of individuals with type 1 diabetes will initially present before diagnosis in type 2 diabetes the acute presentation has a much longer name it's known as hyperosmolar nonketotic state or hhns for short and it's much less common than DKA as it's the initial presentation for only about 2% of individuals with type 2 diabetes now the difference between DKA and hhns has to do with the difference between the underlying mechanisms of type 1 diabetes and type 2 diabetes now the most important difference is that in DKA the individual will become acidotic due to the production of keto acids hence the name diabetic ketoacidosis as opposed to hyperosmolar non-ketotic state where keto acids are not produced now the next way individuals with diabetes can present is what we'll call subacute and this is a mild to moderate presentation the occurs over a period of weeks two months these individuals or maybe someone close to them notice that they are generally just not feeling as well as they normally do and they may experience symptoms of fatigue increased thirst frequent urination or even weight loss now once again this can occur with either type 1 or type 2 diabetes and in type 1 diabetes this is the most common form of presentation before diagnosis accounting for about 70% of individuals with type 1 diabetes and type 2 diabetes this is also common however the predominant symptoms are a little bit more vague and weight loss is less common and the last way individuals with diabetes can present is through asymptomatic screening tests so type 2 diabetes affects nearly 10% of the population and due to this high prevalence potentially severe complications and the relative ease of treatment most adults especially those with the risk factors of type 2 diabetes should be routinely screened for the disease and this is the most common means by which type-2 diabetes is diagnosed however it's rare for the diagnosis of type 1 diabetes as routine screening for type 1 diabetes is not usually performed so let's move on to the diagnostic test for diabetes mellitus regardless of the type of diabetes or the severity of presentation laboratory tests are necessary for the diagnosis of diabetes mellitus so let's briefly review the general mechanism of diabetes to gain a better understanding of the two major laboratory tests that are used to diagnose the disease as the blood glucose levels in the body rise this is sensed by the beta cells in the pancreas which secrete the hormone insulin and insulin then acts on cells throughout the body to take the glucose from the blood up and thus lower the blood glucose levels so in diabetes mellitus regardless of the type this insulin pathway is not working properly therefore the body is not able to lower blood glucose levels and this results in increased blood glucose levels known as hyperglycemia which is the characteristic finding of diabetes mellitus now a side effect of hyperglycemia is a process known as oscillation which is the non-enzymatic attachment of glucose to proteins and one protein that this occurs with that is of importance in diabetes mellitus is the protein hemoglobin which is located within red blood cells and in the presence of hyperglycemia glucose will attach itself to an abnormally high percentage of hemoglobin within the red blood cells and this is known as glycosylated hemoglobin or hemoglobin a1c and it's the hyperglycemia and the hemoglobin a1c that are tested for in the blood to aid in the diagnosis of diabetes mellitus so let's put this diagram over here to the side and discuss a little bit more about these diagnostic tests first let's talk about the three categories of results for the diagnostic tests the first is a normal level the second is the level that's associated with diabetes then in between is a third category and it relates only to type 2 diabetes and it's known as pre-diabetes since type 2 diabetes is a chronic disease that typically takes many years to develop and it's routinely screen for oftentimes individuals will have a test result that is above the normal level however not severe enough to be considered diabetes and this is known as pre-diabetes and it's important because individuals with pre-diabetes as its name suggests are much more likely to develop type 2 diabetes in the future so by identifying them as having pre-diabetes they can start treating the underlying mechanism through lifestyle modifications such as weight loss a proper diet and routine exercise in order to prevent or delay the development of type 2 diabetes in the future now as we mentioned before there are two major types of laboratory tests used to diagnose diabetes mellitus and they are blood glucose levels and hemoglobin a1c the blood glucose level can be measured by many different methods and unfortunately depending on the method the results will vary so the three most common methods are random fasting and a two-hour glucose tolerance test which will just abbreviate GTT now we'll bring in the different diagnostic levels here however the exact No for each of these categories are less important than a couple of trends and the first one is that regardless of the method random fasting or the two-hour glucose tolerance test a blood glucose level of greater than or equal to 200 milligrams per deciliter is consistent with diabetes but this number is slightly lower if fasting blood glucose levels is used then the level is 126 milligrams per deciliter then the last important point to mention is that a random glucose test cannot be used to diagnose pre-diabetes you need either a fasting or a two-hour glucose tolerance test now fortunately hemoglobin a1c testing is a little bit more straightforward as the timing of the test does not matter and then similarly to the blood glucose test there's one important number to remember and that is that a level greater than or equal to six and a half percent is consistent with diabetes mellitus so now that we have a better understanding of the clinical presentation of diabetes mellitus and the laboratory tests let's bring these two components together to discuss how the diagnosis of diabetes mellitus is made neither the presentation or the diagnostic tests alone is enough to diagnose diabetes the diagnosis is made by a combination of the two and there are two ways diabetes mellitus can be diagnosed and they're based on different presentations so first if the individual has symptoms of diabetes whether acute or subacute then only one positive test either the blood glucose or the hemoglobin a1c is necessary for the diagnosis of diabetes mellitus however if the individual is asymptomatic then a diagnosis of diabetes mellitus requires two positive tests that are separated by at least one week of time