Diabetes mellitus (Type 1): Clinical sciences

Diabetes mellitus is a chronic condition where tissue cells can’t properly absorb and use glucose, so it stays and builds up in the blood. Normally, pancreatic islet beta cells produce insulin, which acts on insulin receptors on tissue cells to promote uptake and storage of glucose, amino acids, and triglycerides, as well as stimulate glycolysis, protein synthesis, and lipogenesis.

Now, there are two types of diabetes, type 1 and type 2. In type 1 diabetes, there’s autoimmune destruction of the pancreatic islet beta cells, resulting in severe insulin deficiency and, ultimately, hyperglycemia. This is in contrast to type 2 diabetes mellitus, where the pancreatic islet beta cells stop properly responding to stimulation to produce insulin, combined with insulin resistance, meaning that the tissue cells aren’t able to appropriately respond to the little insulin that’s still being produced.

In either disease type, the resulting hyperglycemia can cause clinical manifestations ranging from prediabetes and diabetes mellitus, to severe life-threatening conditions, like diabetic ketoacidosis, or DKA, most commonly seen in patients with type 1 diabetes, and, hyperosmolar hyperglycemic state, or HHS, most commonly in type 2 diabetes.

Now, if you suspect type 1 diabetes mellitus, you should first perform an ABCDE assessment to determine if your patient is unstable or stable. If the patient is unstable, stabilize the airway, breathing, and circulation. This means that you might need to intubate the patient. Next, obtain IV access and, if your patient is hypotensive, start IV fluids for volume resuscitation. Finally, put your patient on continuous vital sign monitoring, such as pulse oximetry, blood pressure, and heart rate.

Next, you want to assess for DKA or, less frequently, HHS. Obtain a focused history and physical exam, and order labs, such as point-of-care blood glucose, serum osmolality, BMP, urinalysis, hemoglobin A1c, as well as ABG or VBG.

Patients typically present with fatigue, headache, or dry mouth, polyuria, and polydipsia. They may also be so confused they cannot give an accurate history, so be sure to speak with caretakers and review the chart thoroughly to get an accurate history. Your patient may also have had a precipitating illness or infection, or have a known history of diabetes mellitus with or without disruption to their diabetes treatment plan.

On the other hand, physical exam might reveal tachypnea, tachycardia, and hypotension in a confused, somnolent patient. The mucous membranes are often dry. Let’s start by using our labs to help us distinguish between DKA and HSS. In HHS, lab results typically reveal a significantly elevated random blood glucose, more so than DKA, often exceeding 600 milligrams per deciliter. BMP may reveal hyponatremia and hypokalemia, as well as elevated BUN and creatinine. The serum osmolality is high, usually greater than 320 milliosmoles per kilogram. Finally, there will be an elevated hemoglobin A1c.

On the other hand, DKA, lab results reveal a significantly elevated random blood glucose, exceeding 250 milligrams per deciliter. BMP may reveal hyponatremia and hypokalemia, as well as elevated BUN and creatinine. There is a normal serum osmolality. Finally, there will be an elevated hemoglobin A1c, and the ABG or VBG will confirm elevated anion gap metabolic acidosis. You may also see decreased bicarbonate, hinting at a metabolic acidosis. Urinalysis will show ketones.

In either case, HHS or DKA, management of these individuals includes IV fluid resuscitation to correct dehydration and hyperosmolality, as well as electrolyte repletion. Additionally, you can start an IV insulin drip, if indicated, and carefully monitor potassium levels. Don’t forget to treat any underlying or precipitating causes!

Now that we're done with unstable patients, let’s go back to the ABCDE assessment and discuss stable ones. If your patient is stable, first obtain a focused history and physical examination. Your patient might report unintentional weight loss, polydipsia, polyuria, and blurred vision, while family history often reveals autoimmune disorders such as thyroid disease or celiac disease.

On physical exam, you may notice oral thrush or dry mucous membranes. At this point, you should suspect diabetes mellitus, and proceed with labs, such as hemoglobin A1c, a fasting blood glucose, a 2-hour oral glucose tolerance test, or OGTT, and a random blood glucose test. Keep in mind that not all patients require an OGTT; this is often used when the other values are inconclusive or unclear in making a diagnosis.

Now let’s look at lab results to determine a diagnosis. Now, if the hemoglobin A1c is less than 5.7%, fasting blood glucose is less than 100 mg/dL, blood glucose after the 2-hour OGTT is less than 140 mg/dL, and random blood glucose is less than 200 mg/dL, then you should consider an alternative diagnosis.

On the other hand, you should consider prediabetes if the hemoglobin A1c is between 5.7 and 6.5%, fasting blood glucose is between 100 and 126 mg/dL, or blood glucose after the 2-hour OGTT is between 140 and 199, and a random blood glucose is under 200 mg/dL. Keep in mind that prediabetes typically precedes type 2 diabetes mellitus, and only rarely precedes type 1.