Type 1 Diabetes Mellitus Clinical Presentation

Updated: Jul 03, 2023
  • Author: Romesh Khardori, MD, PhD, FACP; Chief Editor: George T Griffing, MD  more...
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The most common symptoms of type 1 diabetes mellitus (DM) are polyuria, polydipsia, and polyphagia, along with lassitude, nausea, and blurred vision, all of which result from the hyperglycemia itself.

Polyuria is caused by osmotic diuresis secondary to hyperglycemia. Severe nocturnal enuresis secondary to polyuria can be an indication of onset of diabetes in young children. Thirst is a response to the hyperosmolar state and dehydration.

Fatigue and weakness may be caused by muscle wasting from the catabolic state of insulin deficiency, hypovolemia, and hypokalemia. Muscle cramps are caused by electrolyte imbalance. Blurred vision results from the effect of the hyperosmolar state on the lens and vitreous humor. Glucose and its metabolites cause osmotic swelling of the lens, altering its normal focal length.

Symptoms at the time of the first clinical presentation can usually be traced back several days to several weeks. However, beta-cell destruction may have started months, or even years, before the onset of clinical symptoms.

The onset of symptomatic disease may be sudden. It is not unusual for patients with type 1 DM to present with diabetic ketoacidosis (DKA), which may occur de novo or secondary to the stress of illness or surgery. An explosive onset of symptoms in a young lean patient with ketoacidosis always has been considered diagnostic of type 1 DM.

Over time, patients with new-onset type 1 DM will lose weight, despite normal or increased appetite, because of depletion of water and a catabolic state with reduced glycogen, proteins, and triglycerides. Weight loss may not occur if treatment is initiated promptly after the onset of the disease.

Gastrointestinal (GI) symptoms of type 1 DM are as follows:

  • Nausea, abdominal discomfort or pain, and change in bowel movements may accompany acute DKA

  • Acute fatty liver may lead to distention of the hepatic capsule, causing right upper quadrant pain

  • Persistent abdominal pain may indicate another serious abdominal cause of DKA (eg, pancreatitis

  • Chronic GI symptoms in the later stage of DM are caused by visceral autonomic neuropathy

Neuropathy affects up to 50% of patients with type 1 DM, but symptomatic neuropathy is typically a late development, developing after many years of chronic prolonged hyperglycemia. Peripheral neuropathy presents as numbness and tingling in both hands and feet, in a glove-and-stocking pattern; it is bilateral, symmetric, and ascending.

History in patients with established diabetes

It is important to inquire about the type and duration of the patient’s diabetes and about the care the patient is receiving for diabetes. Determination of the type of diabetes is based on history, therapy, and clinical judgment. The chronic complications of diabetes are related to the length of time the patient has had the disease.

Ask about the type of insulin being used, delivery system (pump vs injections), dose, and frequency. Also ask about oral antidiabetic agents, if any. Of course, a full review of all medications and over-the-counter supplements being taken is crucial in the assessment of patients with type 1 DM.

Patients using a pump or a multiple-injection regimen have a basal insulin (taken through the pump or with the injection of a long-acting insulin analogue) and a premeal rapid-acting insulin, the dose of which may be determined as a function of the carbohydrate count plus the correction (to adjust for how high the premeal glucose level is). In these patients, ask about the following:

  • Basal rates (eg, units per hour by pump, generally 0.4-1.5 U/h, potentially varying on the basis of time of day); the total daily dose as basal insulin is a helpful value to know

  • Carbohydrate ratio (ie, units of insulin per grams of carbohydrate, generally 1 unit of rapid-acting insulin per 10-15 g carbohydrate)

  • Correction dose (ie, how far the blood glucose level is expected to decrease per unit of rapid-acting insulin, often 1 U of insulin per 50-mg/dL decrease, though individuals with insulin resistance may need 1 U per 25-mg/dL decrease)

  • Some patients may be taking premeal pramlintide (an amylin analogue)

A focused diabetes history should also include the following questions:

  • Is the patient’s diabetes generally well controlled, with near-normal blood glucose levels? (Patients with poorly controlled blood glucose levels heal more slowly and are at increased risk for infection and other complications)

  • Does the patient have severe hypoglycemic reactions? (If the patient has episodes of severe hypoglycemia and therefore is at risk for losing consciousness, this possibility must be addressed, especially if the patient drives)

  • Does the patient have diabetic nephropathy that might alter the use of medications or intravenous (IV) radiographic contrast material?

  • Does the patient have macrovascular disease, such as coronary artery disease (CAD), which should be considered in the emergency department (ED)?

  • Does the patient self-monitor his or her blood glucose levels? (Note the frequency and range of values at each time of day; an increasing number of patients monitor with continuous sensors)

  • When was the patient’s hemoglobin A1c (HbA1c) value (an indicator of long-term glucose control) last measured? What was it?

In assessing glycemic exposure of a patient with established type 1 DM, review of self-monitored blood glucose levels is necessary. Ideally, this done by uploading time- and date-stamped levels from the patient’s meter to assure full understanding of the frequency of testing and the actual levels.

Questions regarding hypoglycemia and hyperglycemia

Hypoglycemia and hyperglycemia should be considered. Ask the following questions as needed:

  • Has the patient experienced recent polyuria, polydipsia, nocturia, or weight loss?

  • Has the patient had episodes of unexplained hypoglycemia? If so, when, how often, and how does the patient treat these episodes?

  • Does the patient have hypoglycemia unawareness (ie, does the patient lack the adrenergic warning signs of hypoglycemia)? (Hypoglycemia unawareness indicates an increased risk of subsequent episodes of hypoglycemia)

Questions regarding microvascular complications

Microvascular complications, such as retinopathy and nephropathy, should be considered as well. Ask the following questions as appropriate:

  • When was the patient’s last dilated eye examination? What were the results?

  • Does the patient have known kidney disease?

  • What were the dates and results of the last measurements of urine protein and serum creatinine levels?

Questions regarding macrovascular complications

Macrovascular complications should be explored. Questions should include the following:

  • Does the patient have hypertension? What medications are taken?

  • Does the patient have symptoms of claudication or a history of vascular bypass?

  • Has the patient had a stroke or transient ischemic attack?

  • What are the patient’s most recent lipid levels?

  • Is the patient taking lipid-lowering medication?

Questions regarding neuropathy

Potential neuropathy should be taken into account. Ask whether the patient has a history of neuropathy or symptoms of peripheral neuropathy or whether autonomic neuropathy is present (including erectile dysfunction if the patient is a man).

Other questions

The possibility of foot disease should be addressed. Inquire as to whether the patient has a history of foot ulcers or amputations or whether any foot ulcers are present. (See Diabetic Foot and Diabetic Foot Infections.)

The possibility of infection also should be considered. Be sure to inquire about whether frequent infections are a problem and, if so, at what sites.


Physical Examination

In new cases of diabetes, physical examination findings are usually normal. Patients with DKA, however, will have Kussmaul respiration, signs of dehydration, hypotension, and, in some cases, altered mental status.

In established cases, patients should be examined every 3 months for macrovascular and microvascular complications. They should undergo funduscopic examination for retinopathy and monofilament testing for peripheral neuropathy.

Diabetes-focused examination

A diabetes-focused physical examination includes assessment of vital signs, funduscopic examination, limited vascular and neurologic examinations, and foot examination. Other organ systems should be assessed as indicated by the patient’s clinical situation. A comprehensive examination is not necessary at every visit.

Assessment of vital signs

Patients with established diabetes and autonomic neuropathy may have orthostatic hypotension. Orthostatic vital signs may be useful in assessing volume status and in suggesting the presence of an autonomic neuropathy. Measurement of the pulse is important, in that relative tachycardia is a typical finding in autonomic neuropathy, often preceding the development of orthostatic hypotension. If the respiratory rate and pattern suggest Kussmaul respiration, DKA must be considered immediately, and appropriate tests must be ordered.

Funduscopic examination

The funduscopic examination should include a careful view of the retina. Both the optic disc and the macula should be visualized. If hemorrhages or exudates are seen, the patient should be referred to an ophthalmologist as soon as possible. Examiners who are not ophthalmologists tend to underestimate the severity of retinopathy, which cannot be evaluated accurately unless the patients’ pupils are dilated.

Foot examination

The dorsalis pedis and posterior tibialis pulses should be palpated and their presence or absence noted. This is particularly important in patients who have foot infections: poor lower-extremity blood flow can delay healing and increase the risk of amputation.

Documenting lower-extremity sensory neuropathy is useful in patients who present with foot ulcers because decreased sensation limits the patient’s ability to protect the feet and ankles. If peripheral neuropathy is found, the patient should be made aware that foot care (including daily foot examination) is very important for the prevention of foot ulcers and lower-extremity amputation. (See Diabetic Foot and Diabetic Foot Infections.)




Infections cause considerable morbidity and mortality in patients with diabetes. Infection may precipitate metabolic derangements, and conversely, the metabolic derangements of diabetes may facilitate infection. (See Infections in Patients with Diabetes Mellitus.)

Patients with long-standing diabetes tend to have microvascular and macrovascular disease with resultant poor tissue perfusion and increased risk of infection. The ability of the skin to act as a barrier to infection may be compromised when the diminished sensation of diabetic neuropathy results in unnoticed injury.

Diabetes increases susceptibility to various types of infections. The most common sites are the skin and urinary tract. Dermatologic infections that occur with increased frequency in patients with diabetes include staphylococcal follicular skin infections, superficial fungal infections, cellulitis, erysipelas, and oral or genital candidal infections. Both lower urinary tract infections and acute pyelonephritis are seen with greater frequency.

A few infections, such as malignant otitis externa, rhinocerebral mucormycosis, and emphysematous pyelonephritis, occur almost exclusively in patients with diabetes, though they are fairly rare even in this population. Infections such as staphylococcal sepsis occur more frequently and are more often fatal in patients with diabetes than in others. Infections such as pneumococcal pneumonia affect patients with diabetes and other patients with the same frequency and severity. [84]


A study reported that out of 178 adult patients hospitalized with coronavirus disease 2019 (COVID-19), at least one underlying condition was found in 89.3%, the most common being hypertension (49.7%), obesity (48.3%), chronic lung disease (34.6%), diabetes mellitus (28.3%), and cardiovascular disease (27.8%). [85]

According to a report by Stokes et al, out of 287,320 US cases of COVID-19 in which the patient’s underlying health status was known, diabetes was the second most common underlying condition (30%), after cardiovascular disease (32%), which in this study included hypertension. [86, 87]

The aforementioned study by Barrera et al found the overall prevalence of diabetes in patients with COVID-19 to be 12%, with the prevalence being 18% in severe COVID-19. [63, 64]

In patients with type 1 DM who were diagnosed with COVID-19, a study by Ebekozien et al found that high blood glucose (48.5%), elevated temperature (45.5%), dry cough (39.4%), excess fatigue (33.3%), vomiting (33.3%), shortness of breath (30.3), nausea (30.2%), and body aches/headaches (21.2%) were the most prevalent presenting symptoms reported. Moreover, diabetic ketoacidosis was the most prevalent adverse outcome (45.5%) among these patients. [88, 89]

The Centers for Disease Control and Prevention (CDC) includes type 2 DM in the list of conditions that increase the likelihood of severe illness in persons with COVID-19, and type 1 DM in the list of conditions that may increase this likelihood. [90]

Ophthalmologic complications

Diabetes can affect the lens, vitreous, and retina, causing visual symptoms that may prompt the patient to seek emergency care. Visual blurring may develop acutely as the lens changes shape with marked changes in blood glucose concentrations.

This effect, which is caused by osmotic fluxes of water into and out of the lens, usually occurs as hyperglycemia increases, but it also may be seen when high glucose levels are lowered rapidly. In either case, recovery to baseline visual acuity can take up to a month, and some patients are almost completely unable to read small print or do close work during this period.

Patients with diabetes tend to develop senile cataracts at a younger age than persons without diabetes. Rarely, patients with type 1 DM that is very poorly controlled (eg, those with frequent episodes of DKA) can acutely develop a “snowflake” (or “metabolic”) cataract. Named for their snowflake or flocculent appearance, these cataracts can progress rapidly and create total opacification of the lens within a few days.

Whether diabetes increases the risk of glaucoma remains controversial; epidemiologic studies have yielded conflicting results. [91] Glaucoma in diabetes relates to the neovascularization of the iris (ie, rubeosis iridis diabetica).

Diabetic retinopathy is the principal ophthalmologic complication of DM. (See Diabetic Retinopathy.) Diabetic retinopathy is the leading cause of blindness in the United States in people younger than 60 years and affects the eyes in the following different ways:

  • Background retinopathy involves retinal small vessel abnormality leading to hard exudates, hemorrhages, and microaneurysms; it does not affect acuity

  • Proliferative retinopathy involves extensive proliferation of new retinal small blood vessels; a sudden loss of vision can occur because of vitreous hemorrhage from proliferating new vessels or retinal detachment

  • Maculopathy involves edema and hard exudate or retinal ischemia; it causes a marked reduction of acuity

Whether patients develop diabetic retinopathy depends on the duration of their diabetes and on the level of glycemic control. [92, 93, 94] The following are the 5 stages in the progression of diabetic retinopathy:

  1. Dilation of the retinal venules and formation of retinal capillary microaneurysms

  2. Increased vascular permeability

  3. Vascular occlusion and retinal ischemia

  4. Proliferation of new blood vessels on the surface of the retina

  5. Hemorrhage and contraction of the fibrovascular proliferation and the vitreous

The first 2 stages of diabetic retinopathy are jointly referred to as background or nonproliferative retinopathy. Initially, the retinal venules dilate, then microaneurysms (tiny red dots on the retina that cause no visual impairment) appear. The microaneurysms or retinal capillaries become more permeable, and hard exudates appear, reflecting leakage of plasma.

Rupture of intraretinal capillaries results in hemorrhage. If a superficial capillary ruptures, a flame-shaped hemorrhage appears. Hard exudates are often found in partial or complete rings (circinate pattern), which usually include multiple microaneurysms. These rings usually mark an area of edematous retina.

The patient may not notice a change in visual acuity unless the center of the macula is involved. Macular edema can cause visual loss; therefore, all patients with suspected macular edema must be referred to an ophthalmologist for evaluation and possible laser therapy. Laser therapy is effective in decreasing macular edema and preserving vision but is less effective in restoring lost vision. (See Macular Edema in Diabetes .)

Preproliferative (stage 3) and proliferative diabetic retinopathy (stages 4 and 5) are the next phases in the progression of the disease. Cotton-wool spots can be seen in preproliferative retinopathy. These represent retinal microinfarcts from capillary occlusion and appear as off-white to gray patches with poorly defined margins.

Proliferative retinopathy is characterized by neovascularization, or the development of networks of fragile new vessels that often are seen on the optic disc or along the main vascular arcades. The vessels undergo cycles of proliferation and regression. During proliferation, fibrous adhesions develop between the vessels and the vitreous. Subsequent contraction of the adhesions can result in traction on the retina and retinal detachment. Contraction also tears the new vessels, which hemorrhage into the vitreous.

Diabetic nephropathy

About 20–30% of patients with type 1 DM develop evidence of nephropathy, [95] and all patients with diabetes should be considered to have the potential for renal impairment unless proven otherwise. Chronically elevated blood pressure contributes to the decline in renal function. The use of contrast media can precipitate acute renal failure in patients with underlying diabetic nephropathy. Although most recover from contrast medium–induced renal failure within 10 days, some have irreversible renal failure. (See Diabetic Nephropathy.)

Diabetic neuropathy

In the peripheral nerves, diabetes causes peripheral neuropathy. (See Diabetic Lumbosacral Plexopathy and Diabetic Neuropathy.) The 4 types of diabetic neuropathy are as follows:

  • Peripheral distal symmetrical polyneuropathy, predominantly sensory

  • Autonomic neuropathy

  • Proximal painful motor neuropathy

  • Cranial mononeuropathy (ie, cranial nerve III, IV, or VI)

Of these 4 types, distal symmetric sensorimotor polyneuropathy (in a glove-and-stocking distribution) is the most common. [96] Besides causing pain in its early stages, this type of neuropathy eventually results in the loss of peripheral sensation. The combination of decreased sensation and peripheral arterial insufficiency often leads to foot ulceration and eventual amputation.

Acute-onset mononeuropathies in diabetes include acute cranial mononeuropathies, mononeuropathy multiplex, focal lesions of the brachial or lumbosacral plexus, and radiculopathies. Of the cranial neuropathies, the third cranial nerve (oculomotor) is most commonly affected, followed by the sixth nerve (abducens) and the fourth nerve (trochlear).

Patients can present with diplopia and eye pain. In diabetic third-nerve palsy, the pupil is usually spared, whereas in third-nerve palsy due to intracranial aneurysm or tumor, the pupil is affected in 80-90% of cases.

It is important to consider nondiabetic causes of cranial nerve palsies, including intracranial tumors, aneurysms, and brainstem stroke. [97] Therefore, evaluation should include nonenhanced and contrast-enhanced compute4d tomography (CT) or, preferably, magnetic resonance imaging (MRI). Neurologic consultation is recommended. Acute cranial-nerve mononeuropathies usually resolve in 2-9 months. Acute thrombosis or ischemia of the blood vessels supplying the structure involved is thought to cause these neuropathies.

Macrovascular complications

People with diabetes experience accelerated atherosclerosis, affecting the small arteries of the heart, brain, lower extremity, and kidney. Coronary atherosclerosis often occurs at a younger age and is more severe and extensive than in those without diabetes, increasing the risk of ischemic heart disease. Atherosclerosis of the internal carotid and vertebrobasilar arteries and their branches predisposes to cerebral ischemia.

Severe atherosclerosis of the iliofemoral and smaller arteries of the lower legs predisposes to gangrene. Ischemia of a single toe or ischemic areas on the heel are characteristic of diabetic peripheral vascular disease; these result from the involvement of much smaller and more peripheral arteries.

Atherosclerosis of the main renal arteries and their intrarenal branches causes chronic nephron ischemia, which is a significant component of multiple renal lesions in diabetes. However, not all people with type 1 DM are at risk for nephropathy, because there are some polymorphisms in the various factors involved in its pathogenesis, which can modulate the course of this disease from one person to the other.

Risk factors for macrovascular disease

Macrovascular disease is the leading cause of death in patients with diabetes, causing 65-75% of deaths in this group, compared with approximately 35% of deaths in people without diabetes. Diabetes by itself increases the risk of myocardial infarction (MI) 2-fold in men and 4-fold in women, and many patients have other risk factors for MI as well.

The HbA1c value per se, rather than self-reported diabetes status or other established risk factors, robustly predicts MI odds. Each 1% increment in HbA1c independently predicts 19% higher odds for MI. [98] The risk of stroke in people with diabetes is double that of nondiabetic people, and the risk of peripheral vascular disease is 4 times that of people without diabetes.

Patients with diabetes may have an increased incidence of silent ischemia. [99] Diastolic dysfunction is common in patients with diabetes and should be considered in patients who have symptoms of congestive heart failure and a normal ejection fraction.