Diabetes: Symptoms & Diagnosis

By Edo Paz, MD
Medically reviewed checkmarkMedically reviewed
September 26, 2019

Diabetes mellitus refers to a group of disorders characterized by high levels of sugar (glucose) in the blood. There are two main types of diabetes—type 1 and type 2—differentiated from one another by the underlying cause of the disease.

Around 90% of cases diagnosed in adulthood are type 2 diabetes. Many sufferers don’t know they have diabetes because symptoms are often mild, or non-existent, in the early stages. This article will help you learn what to look out for so you can decide if you need to take further action.

What Is Diabetes

Diabetes is a disease that impairs the body’s ability to produce the hormone insulin and regulate blood sugar levels. This can result in higher than normal glucose levels and abnormal metabolism of carbohydrates. You will likely find out you have diabetes because your blood glucose is higher than the norm. Your doctor might discover this in a routine blood test, or you may suspect diabetes if you are showing some of the symptoms.

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Behind the scenes, a series of events in your body has caused your blood glucose to rise. Glucose enters your bloodstream from the food you eat and is the primary source of energy for your muscles, tissues, and brain. A healthy pancreas secretes insulin – a hormone responsible for driving glucose into the cells so it can be used by the body to provide energy. Diabetes occurs when the pancreas either stops producing insulin at all, or it produces insulin, but the body no longer responds to it. Lack of insulin or impaired insulin response causes blood sugar to rise. If it rises to a high enough level, you are considered to have diabetes. The way in which the normal insulin-glucose response is impaired determines which type of diabetes you have:

  • Type 1 diabetes: Your body does not make enough, or any, insulin so the glucose you consume stays in your blood and can not reach your cells.
  • Type 2 diabetes: Your pancreas produces insulin, however, your body has become insensitive to it and glucose remains in the bloodstream and is not efficiently shunted into the cells.

There are also two other classifications of diabetes, both of which may be reversed with lifestyle changes and medication.

  • Prediabetes: This is when your blood sugar levels are higher than normal (usually due to the body becoming less responsive to insulin), but not high enough to be classified as diabetes.
  • Gestational diabetes: Some pregnant women experience diabetes while pregnant, but this condition usually resolves after the baby is delivered. However, these women are an increased risk of developing diabetes over the coming years.

Over time, higher than normal levels of blood glucose can cause health problems, so it is important to begin a treatment plan as early as possible. You can learn about treatment options for diabetes in part two of this series about diabetes.

Diabetes is a chronic (long-term) disorder that is considered incurable, although a combination of medication, lifestyle adjustments, and other interventions can allow you to successfully manage the disease, avoid further complications, and enjoy a normal life-span.

Diabetes Insipidus

Please note that if you have been diagnosed with diabetes insipidus, this is a very different condition from diabetes mellitus (the type of diabetes we are discussing in this article). Diabetes insipidus is a rare disorder that causes an imbalance of fluids in the body. While some of its symptoms – such as extreme thirst and the need to urinate often – are similar to those of diabetes, the two conditions are not related and should not be confused.

Did You Know?

  • ~30.3 million Americans (9.4% of the population) had diabetes in 2015.
  • 7.2 million (23.8%) of them didn’t know it.

What Is Prediabetes?

In prediabetes, also known as impaired glucose tolerance, your blood sugar is higher than normal but not yet high enough to be considered diabetes. There are various ways to diagnose prediabetes, but one of them is to measure the blood sugar level when a patient has been fasting. The classification is as follows:

  • Normal: less than 100 mg/dL (5.6 mmol/L)
  • Prediabetes:100 to 125 mg/dL (5.6 to 6.9 mmol/L)
  • Diabetes: 126 mg/dL (7 mmol/L) or higher, on two separate tests

In prediabetes, your pancreas secretes insulin but your cells are not responding to the hormone in the normal way and your body is beginning to struggle with glucose control. At this stage, you may not notice any symptoms and you may be unaware that you are in the early stages of the disease. If you have risk factors for diabetes, such as being overweight, over 45, and sedentary, you can ask your doctor to perform a simple blood sugar test. Your doctor can also order a test called the A1C blood test, which provides an estimate of what your glucose levels have been over the previous three months. This test can be a useful predictor of diabetes risk. If you are diagnosed with prediabetes, it could be considered a wake-up call, since you can implement lifestyle changes that may prevent you from getting the full-blown disease.

What Is Type 1 Diabetes?

About ~5% of people with diabetes have type 1. Type 1 diabetes is an autoimmune condition where the body attacks and destroys the insulin-producing beta cells in the pancreas, so they can no longer produce insulin. Scientists think a combination of genetic and environmental factors might trigger the disease.

Type 1 diabetes is often referred to as juvenile-onset diabetes because it often begins in childhood. Many children who develop type 1 diabetes have a genetic predisposition, although this is not true in every case. While type 1 usually begins in childhood, it can start at any age. Sometimes, adults are mistakenly diagnosed with type 2 diabetes when they actually have type 1, but your doctor will be able to carry out the appropriate tests to correctly diagnose your condition.

What Is Type 2 Diabetes?

Type 2 diabetes is the most common form of diabetes. It is usually discovered when blood glucose is found to be too high in a routine test. In type 2 diabetes, the pancreas either does not make enough insulin or your body’s cells cannot use insulin properly. Because of this, glucose stays in your bloodstream and isn’t distributed to your cells where it is needed for energy. Type 2 diabetes is thought to be triggered by several factors, including lifestyle and genetics.

The condition usually begins with insulin resistance, a state where muscle, liver, and fat cells do not respond to insulin efficiently and glucose, in turn, does not go into the cells. The body starts to produce more insulin in an attempt to get the cells to take the excess glucose. Over time, the pancreas cannot keep up with such high levels of insulin production, and blood glucose levels rise.

You are more likely to develop type 2 diabetes if you have some of the risk factors outlined here. The good news is that in many cases, it is possible to prevent or delay the development of type 2 diabetes by taking the necessary precautions and making lifestyle changes such as losing weight or becoming more physically active.

What Is Gestational Diabetes

Pregnant women in the United States are offered blood glucose screening as part of their routine pregnancy care. If you have not previously suffered from diabetes, but develop high fasting blood sugar during pregnancy you probably have gestational diabetes. Nearly 10% of pregnancies in the U.S. are affected by gestational diabetes, so you are not alone.

Scientists believe gestational diabetes is caused by the hormonal changes of pregnancy, along with genetic and lifestyle factors. Some hormones produced during pregnancy are involved in insulin resistance. The majority of pregnant women can create enough insulin to counteract insulin resistance. However, some can’t, resulting in gestational diabetes.

Gestational diabetes is usually temporary and resolves after pregnancy is over. However, it can persist, and women who have had gestational diabetes are at an increased risk of developing type-2 diabetes in the future. There may be no symptoms at all and you may only discover you have gestational diabetes from a routine prenatal blood test.

Alternatively, you may experience some of the following symptoms:

There is a correlation between weight and gestational diabetes, with women who are overweight or obese having a higher risk of developing gestational diabetes when pregnant.

If you’re diagnosed with gestational diabetes, it is important to work with your doctor to ensure that you and your baby stay healthy. Women with gestational diabetes are at a higher risk for developing preeclampsia, depression, and needing a Caesarean section. Babies born to mothers with poorly-managed gestational diabetes are often larger than normal at birth and are more likely to have low blood sugar or be jaundiced.

Gestational diabetes is treatable and working with your health-care team can help you ensure a healthy pregnancy. Treatment for gestational diabetes focuses on keeping your blood sugar levels normal through dietary intervention and regular physical activity. If these interventions do not control the blood sugar levels, insulin or other medications can be used. About 50% of women with gestational diabetes go on to develop type 2 diabetes.

If you were overweight prior to pregnancy, have polycystic ovary syndrome (PCOS), had gestational diabetes in a previous pregnancy or have a family history of type 2 diabetes, your chances of getting gestational diabetes are higher than average. High-risk women should have their blood glucose tested at the first prenatal visit and then monitored regularly throughout the pregnancy. Your doctor will advise you about the necessary schedule of check-ups and can help you develop a meal plan that makes sense for you.

Other Causes of Diabetes

Less commonly, diabetes can be triggered by a genetic mutation, certain diseases, damage to the pancreas, or by taking some medications. Here are some of the main alternative causes of diabetes you should be aware of:

  • Genetics: Mutations or changes to one or more genes can cause diabetes. Genetic mutations are usually passed on through families but sometimes occur randomly.
  • Cystic fibrosis: A condition where the body produces a thick mucus that can, in some cases, scar the pancreas and prevent it from making enough insulin.
  • Hemochromatosis: A condition in which the body both absorbs and then stores an abundance of iron. It can cause damage to the body’s organs if left untreated.
  • Damage to the pancreas: Pancreatic conditions, such as pancreatic cancer, have the potential to hurt the beta cells or hamper their ability to create insulin. This can result in diabetes.

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Hormonal Diseases

Hormonal diseases that can cause diabetes include:

  • Acromegaly: Acromegaly is when the body produces an excessive amount of growth hormone (GH). Symptoms can include joint aches, swelling of the feet and hands, and excessive growth of cartilage and bone.
  • Hyperthyroidism: Hyperthyroidism occurs when the thyroid gland creates too much of the hormone thyroxine. Symptoms include increased appetite, weight loss, and rapid heart beat.
  • Cushing’s Syndrome: Cushing’s Syndrome happens over a period of time, when the body creates too much cortisol. Symptoms include weight gain, weak muscles, and a round face.


Some medicines can harm beta cells or disrupt the way insulin works. If you are on any of the following medications and have concerns about side-effects, discuss these with your doctor:

Niacin, a type of vitamin B3

  • Some diuretics
  • Some anti-seizure drugs
  • Psychiatric drugs, including clozapine, olanzapine, risperidone, and quetiapine.
  • Drugs used to treat HIV
  • Pentamidine, used to treat a type of pneumonia
  • Glucocorticoids, used to treat inflammatory illnesses such as rheumatoid arthritis, asthma, lupus, and ulcerative colitis
  • Anti-rejection medicines used after a transplant
  • Statins e.g. atorvastatin (Lipitor), simvastatin (Zocor) and pitavastatin (Livalo)

Note: Statins are commonly prescribed to reduce LDL (“bad”) cholesterol levels, and lowering the risk of heart disease and stroke. While statins can, in rare cases, trigger diabetes, the benefits of taking them often outweigh the small chance that you could develop diabetes.

Diabetes Symptoms

Diabetes symptoms vary depending on the level of sugar in your blood. Some people—especially those with prediabetes or type 2 diabetes—may not initially experience any symptoms. In type 1 diabetes, symptoms can happen rapidly and are generally more pronounced.

Some of the indicators of type 1 and type 2 diabetes include:

  • Frequent urge to urinate
  • Extreme thirst
  • Constantly feeling hungry
  • Exhaustion
  • Blurry vision
  • Cuts and bruises that heal slowly
  • Weight loss, though you are still eating (type 1)
  • Discomfort, numbness, or tingling in the hands/feet (type 2)
  • Irritability
  • Frequent infections, particularly in gums, skin or vagina

Diabetes in Children

It is important to be aware that children can get either type 1 or type 2 diabetes, too. If you are caring for a child who starts showing symptoms such as frequent urination, a need to drink excessive amounts, weight-loss, and unusual fatigue or sickness, this can indicate that the child has diabetes. A potty-trained child who is usually dry at night but starts having frequent accidents may also have diabetes.

While type 2 diabetes more commonly occurs in adulthood, cases in childhood are on the rise, fueled by the high incidence of obesity in the population. Be on the lookout for diabetes symptoms in any children under your care and speak to your doctor if you have concerns.

If you suspect your child might have diabetes, take them to a doctor as soon as possible. Your doctor will perform blood tests and other checks to quickly assess the child’s condition. Prompt medical attention is important as, in rare cases, children can develop diabetic ketoacidosis (DKA), a condition where lack of insulin causes a dangerous build-up of acidic ketones in the blood. Diabetic ketoacidosis is a medical emergency that usually requires hospitalization and immediate treatment with insulin and IV fluids.

Early diagnosis and treatment of diabetes will lead to the best outcome in children, so follow up any suspicions immediately. Raising awareness that young children can develop diabetes will help parents know what symptoms to look out for.

How Is Diabetes Diagnosed?

Most people discover their diabetes when they experience symptoms or during routine screening tests. Because of the prevalence of diabetes in the population, particularly amongst at-risk groups, the American Diabetic Association (ADA) recommends that the following people be tested regularly for diabetes:

  • Individuals older than 45 should get an initial blood sugar screening. If the results appear normal, they should be monitored every three years.
  • People with a body mass index higher than 25 (23 for Asian-Americans), regardless of age, who also have added risk factors. These can include atypical cholesterol levels, sedentary lifestyle, elevated blood pressure, etc.
  • Woman who have had gestational diabetes should be tested every three years.
  • Anyone with prediabetes should be tested yearly.

If you suspect you have diabetes or are being screened because you are at risk, your doctor may order one of the following tests:

  • Random blood sugar test: You’ll have a blood test administered outside of your regular testing period. It is helpful for individuals who need a quick diagnosis, as it doesn’t involve fasting or monitoring throughout the day.
  • Fasting blood sugar test: This test is done in the morning, prior to eating or drinking. If your blood sugar tests high it can mean diabetes or insulin resistance. If it tests low, it could be due to your diabetes medication.
  • Glycated hemoglobin (A1C) test: This test monitors your blood sugar levels during a period of two to three months. The higher your A1C levels, the worse your blood sugar control, which can increase the risk of developing diabetes.
  • Urine test: A urine test will look for ketones in the urine, which can be used to evaluate high blood sugar levels. Ketones are chemicals made by the liver. Their levels increase when there isn’t enough insulin to use available glucose.
  • Blood tests: If type 1 diabetes is suspected, your doctor may also likely run a test to look for the presence of the destructive immune system cells (autoantibodies) associated with type 1 diabetes.

Diabetes Risk Factors

The following risk factors make developing type 1 diabetes more likely:

  • Family history: Especially if you have a parent or sibling with type 1.
  • Age: Type 1 diabetes usually develops in children younger than 14 years old and although it can occur at any age, the chances are lower the older you get.
  • Genetics: Having certain genes may increase the risk of getting type 1 diabetes. Your doctor can advise on how to check for these genes.

The following risk factors increase your likelihood of developing type 2 diabetes:

  • Being overweight or obese: Extra weight can cause or exacerbate insulin resistance, and the location of body fat also has an effect. Excess belly fat is connected to type 2 diabetes, insulin resistance, and blood and heart vessel disease.
  • Age: You are at greater risk of getting diabetes if you are over the age of 45.
  • Family history: Having a family member, a parent, or sibling with type 2 diabetes increases your risk.
  • Genetics: Although research is still ongoing, certain genes are associated with developing diabetes. Genes can also increase the risk of type 2 diabetes by predisposing you to weight gain and obesity.
  • Background: African Americans, Alaskan Natives, American Indians, Asian Americans, Hispanics/Latinos, Native Hawaiians, and Pacific Islanders demonstrate a higher incidence of diabetes.

You are also at greater risk of getting type 2 diabetes if you have:

The following risk factors are associated with the development of gestational diabetes:

  • Age > 35
  • Being overweight or obese
  • Excessive gestational weight gain
  • Excessive central body fat deposition
  • Family history of diabetes
  • Short stature (<5 ft)
  • Excessive fetal growth
  • Preeclampsia
  • Gestational hypertension
  • Polycystic ovary syndrome (PCOS)

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Complications from Diabetes

Diabetes is associated with increased risk for other medical conditions. High blood glucose can damage the tiny blood vessels in the eyes, nerves, heart, kidneys, and nervous system leading to some of the complications listed below. Your chance of developing any complications, however, will be greatly lowered if you make the necessary lifestyle modifications or take the needed medications to control your blood sugar. Read our follow-up article and check with your doctor to learn how you can prevent complications.

If your diabetes is poorly-managed, you may be at risk of developing the following complications:

  • Heart disease: Higher than average risk of developing heart disease at a younger age than the rest of the population due to high blood glucose damaging blood vessels in and around the heart.
  • Stroke: Increased risk of stroke (up to 1.5 times higher than non-diabetic people) due to the negative effect of frequent shifts in blood sugar levels on the cardiovascular system.
  • Kidney disease: High blood sugar levels can damage your kidneys causing a condition called diabetic nephropathy.
  • Diabetic eye disease: Over time, diabetes can damage your eyes causing conditions such as diabetic retinopathy, diabetic macular edema, cataracts, and glaucoma.
  • Dental disease: Diabetes can reduce the blood supply to the gums making dental problems, such as gum and bone infections, more likely. High blood sugar may also cause dry mouth and exacerbate gum disease.
  • Nerve damage (diabetic neuropathy): This is a type of nerve damage that can occur in diabetic patients. Symptoms of diabetic neuropathy include pain and numbness in the limbs, cramps, increased sensitivity to touch, muscle weakness, digestive problems, and a tingling or burning sensation in the affected part of the body.
  • Foot problems: Although not specific to diabetes, foot problems such as bunions, corns, calluses, hammertoes, fungal infections, dryness of the skin, and ingrown toenails may occur more commonly in diabetic patients due to the nerve and vascular damage caused by diabetes.
  • Diabetic ketoacidosis: This is a serious complication of diabetes that occurs when your body produces high levels of blood acids called ketones. Symptoms of DKA develop quickly, often within 24 hours, and may include frequent urination, extreme thirst, nausea or vomiting, abdominal pain, confusion, fruity-smelling breath, fatigue, rapid breathing, and dry mouth or skin.

When to See a Doctor

If you experience diabetes symptoms, or if you suspect your child may have diabetes, see your doctor as soon as possible. The earlier your condition is diagnosed, the sooner treatment can begin.

If you have already been diagnosed with diabetes, you will need close medical follow-up until your blood sugar levels stabilize. Your doctor can advise you about which checks you will need and on a suitable schedule of appointments.

If you suspect diabetic ketoacidosis, a rare and dangerous complication of diabetes, go to the emergency room immediately.

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K Health articles are all written and reviewed by MDs, PhDs, NPs, or PharmDs and are for informational purposes only. This information does not constitute and should not be relied on for professional medical advice. Always talk to your doctor about the risks and benefits of any treatment.

Edo Paz, MD

Edo Paz is the VP of Medical at K Health. Dr. Paz has two degrees in chemistry from Harvard and earned his medical degree from Columbia University. He did his medical training in internal medicine and cardiology at New York-Presbyterian. In addition to his work at K Health, Dr. Paz is a cardiologist at White Plains Hospital, part of the Montefiore Health System.