Approximately 38 million Americans have diabetes, and a staggering 8.7 million of them — nearly 1 in 4 — are undiagnosed, according to the CDC’s National Diabetes Statistics Report. Another 98 million adults have prediabetes, the metabolic precursor that often produces no symptoms at all. Recognizing the symptoms of diabetes early is critical because timely intervention can prevent or delay the serious complications — nerve damage, kidney disease, vision loss, cardiovascular disease — that uncontrolled blood sugar causes over time.
For more on common medical conditions and their warning signs, visit our medical conditions guide.
Type 1 vs. Type 2: A Quick Overview
Diabetes is not a single disease. Understanding the difference between Type 1 and Type 2 helps explain why symptoms appear differently and at different speeds.
Type 1 diabetes is an autoimmune condition in which the immune system destroys the insulin-producing beta cells in the pancreas. It accounts for roughly 5-10% of all diabetes cases and is most commonly diagnosed in children, teens, and young adults — though it can develop at any age. Symptoms tend to appear suddenly, often over a matter of weeks, because insulin production drops rapidly.
Type 2 diabetes develops when the body becomes resistant to insulin and the pancreas gradually loses the ability to produce enough insulin to compensate. It accounts for 90-95% of cases and is strongly associated with excess weight, physical inactivity, and family history. Symptoms develop gradually — often over years — which is why so many cases go undetected. The NIDDK notes that Type 2 symptoms can be so subtle that some people have diabetes for years before diagnosis.
Classic Symptoms Shared by Both Types
Despite their different mechanisms, Type 1 and Type 2 diabetes produce many of the same symptoms when blood glucose levels rise above normal. These “classic” symptoms result from excess sugar in the bloodstream and the body’s attempts to compensate.
Excessive Thirst (Polydipsia)
When blood sugar levels are elevated, your kidneys work overtime to filter and absorb the excess glucose. When they can’t keep up, the surplus sugar spills into your urine, pulling fluid from your tissues along with it. This fluid loss triggers intense, persistent thirst — the kind that doesn’t fully resolve no matter how much water you drink.
Frequent Urination (Polyuria)
The flip side of excessive thirst: you’re urinating far more often than normal, sometimes waking multiple times during the night (nocturia). This happens because the kidneys are producing extra urine to flush out the excess glucose. Parents of children developing Type 1 often notice increased bedwetting as an early sign.
Unexplained Weight Loss
Despite eating normally or even more than usual, you lose weight. This symptom is more dramatic in Type 1, where the body — unable to use glucose for energy due to absent insulin — breaks down fat and muscle for fuel instead. Weight loss of 10-20 pounds over a few weeks without dietary changes is a red flag, particularly in younger patients. In Type 2, weight loss is typically less pronounced but can still occur.
Extreme Hunger (Polyphagia)
Without enough insulin to move glucose into cells, your tissues become energy-starved — even when blood sugar levels are high. The brain interprets this cellular starvation as hunger, driving you to eat more. The paradox of diabetes: blood sugar is elevated, but cells are starving.
Fatigue
When cells can’t access glucose efficiently, energy production suffers. Persistent, unexplained fatigue — the kind that isn’t relieved by rest — is one of the most commonly reported early symptoms across both types. Dehydration from polyuria compounds the exhaustion.
Symptoms More Common in Type 2 Diabetes
Because Type 2 develops gradually, some symptoms are chronic, low-grade issues that people learn to live with before connecting them to blood sugar.
Slow-Healing Wounds
Elevated blood sugar impairs blood flow and damages nerves, both of which slow the healing process. Cuts, bruises, and sores that take noticeably longer to heal — particularly on the feet and lower legs — are a classic Type 2 red flag. The Mayo Clinic lists slow-healing sores as a key symptom to watch for.
Frequent Infections
High blood sugar weakens the immune response. People with undiagnosed Type 2 diabetes may experience recurring urinary tract infections, yeast infections (particularly vaginal yeast infections in women), and skin infections. If you’re getting infections more frequently than seems normal, it’s worth checking your blood sugar.
Tingling or Numbness in Hands and Feet
Diabetic neuropathy — nerve damage caused by prolonged high blood sugar — often starts in the extremities. Tingling, pins-and-needles sensations, or numbness in the fingers and toes can be an early sign, though by the time these symptoms appear, nerve damage has already begun. An estimated 50% of people with diabetes develop neuropathy over time, per the NINDS.
Blurred Vision
High blood sugar causes the lens of the eye to swell, changing its shape and affecting your ability to focus. Vision may be intermittently blurry. If caught early and blood sugar is controlled, the vision changes can reverse. However, prolonged uncontrolled diabetes can cause diabetic retinopathy — permanent damage to the retinal blood vessels and a leading cause of blindness.
Darkened Skin Patches (Acanthosis Nigricans)
Velvety, darkened patches of skin in the folds and creases of the body — particularly the neck, armpits, and groin — can be an outward marker of insulin resistance. This condition, called acanthosis nigricans, is especially common in people with prediabetes and early Type 2 diabetes.
Symptoms More Common in Type 1 Diabetes
Type 1 symptoms develop rapidly — over days to weeks — and tend to be more acute.
Nausea, Vomiting, and Abdominal Pain
These can be signs of diabetic ketoacidosis (DKA), a dangerous complication that occurs when the body breaks down fat for fuel at an accelerated rate, producing ketones that make the blood acidic. DKA is more common in Type 1 and can be the presenting symptom at initial diagnosis.
Fruity-Smelling Breath
The ketones produced during fat breakdown include acetone, which gives the breath a distinctive fruity or nail-polish-like odor. This is a warning sign of DKA and requires immediate medical attention.
Mood Changes and Irritability
Children and adolescents developing Type 1 diabetes may become unusually irritable, moody, or have difficulty concentrating — sometimes before the physical symptoms become obvious. These changes are linked to blood sugar fluctuations and cellular energy deprivation in the brain.
When to seek emergency care: Call 911 or go to the nearest emergency room if you or someone you know experiences fruity-smelling breath with nausea and vomiting, confusion or difficulty staying conscious, rapid deep breathing (Kussmaul respirations), severe abdominal pain, or a blood glucose reading above 300 mg/dL with any of these symptoms. Diabetic ketoacidosis is a medical emergency that can progress to coma and death within hours without treatment.
Gestational Diabetes
Gestational diabetes develops during pregnancy, typically in the second or third trimester, and usually produces no noticeable symptoms. It’s detected through routine glucose screening between weeks 24 and 28 of pregnancy. Risk factors include being over 25, excess weight before pregnancy, family history of Type 2 diabetes, and certain ethnic backgrounds (Hispanic, Black, Native American, Asian American). The American College of Obstetricians and Gynecologists recommends screening for all pregnant women.
While gestational diabetes typically resolves after delivery, it increases the mother’s lifetime risk of developing Type 2 diabetes by 50% or more.
Long-Term Complications of Undiagnosed Diabetes
Understanding what uncontrolled blood sugar does to the body over time reinforces why early symptom recognition matters. Many people are diagnosed with Type 2 diabetes only after a complication develops — a sobering reminder that the absence of obvious symptoms doesn’t mean the disease is absent.
Cardiovascular Disease
Adults with diabetes are 2 to 4 times more likely to die from heart disease than adults without diabetes, according to the American Heart Association. Chronically elevated blood sugar damages blood vessel walls and accelerates atherosclerosis (plaque buildup in arteries), increasing the risk of heart attack and stroke.
Diabetic Kidney Disease (Nephropathy)
Diabetes is the leading cause of kidney failure in the United States. High blood sugar damages the kidney’s filtering units (glomeruli) over time, initially causing protein to leak into the urine (microalbuminuria) and eventually reducing kidney function. About 1 in 3 adults with diabetes has some degree of kidney disease, per the NIDDK.
Diabetic Retinopathy
Elevated blood sugar damages the tiny blood vessels in the retina, leading to diabetic retinopathy — the leading cause of new blindness in adults aged 20-74. Early stages produce no symptoms, which is why annual dilated eye exams are recommended for all people with diabetes. Caught early, laser treatment and anti-VEGF injections can prevent progression.
Nerve Damage and Foot Complications
Diabetic neuropathy can affect the feet to the point where injuries go unnoticed. Combined with poor circulation, this creates a dangerous situation: small cuts or blisters become infected, infections spread, and in the worst cases, amputation becomes necessary. Diabetes accounts for more than 60% of non-traumatic lower-limb amputations in the US. Daily foot inspection is one of the simplest and most important self-care habits for people with diabetes.
Getting Tested: What to Expect
If you suspect diabetes, several blood tests can confirm or rule it out:
- Fasting plasma glucose (FPG): Blood drawn after an 8-hour fast. Normal is below 100 mg/dL; 100-125 indicates prediabetes; 126+ on two separate tests indicates diabetes.
- A1C test (glycated hemoglobin): Reflects average blood sugar over the past 2-3 months. Normal is below 5.7%; 5.7-6.4% indicates prediabetes; 6.5%+ indicates diabetes.
- Oral glucose tolerance test (OGTT): Blood sugar is measured 2 hours after drinking a glucose solution. Used for gestational diabetes screening and some diagnostic situations.
- Random plasma glucose: A blood sugar of 200 mg/dL or higher with classic symptoms (thirst, polyuria, weight loss) is diagnostic regardless of when you last ate.
The American Diabetes Association recommends screening for all adults starting at age 35, or earlier if you have risk factors such as obesity, family history, or a history of gestational diabetes.
Frequently Asked Questions
Can you have diabetes and not know it?
Yes — this is extremely common with Type 2 diabetes. The symptoms develop so gradually that many people have had elevated blood sugar for years before diagnosis. The CDC estimates that approximately 22% of adults with diabetes in the US are currently undiagnosed. Regular screening is the only reliable way to catch it early.
What’s the difference between prediabetes and diabetes?
Prediabetes means your blood sugar is higher than normal but not yet in the diabetic range (fasting glucose 100-125 mg/dL or A1C 5.7-6.4%). Without intervention, 15-30% of people with prediabetes develop Type 2 diabetes within 5 years, per the CDC. Lifestyle changes — modest weight loss, regular exercise, dietary improvements — can reduce that risk by up to 58%.
Can diabetes be cured?
Type 1 diabetes currently has no cure and requires lifelong insulin therapy. Type 2 diabetes can be put into remission in some cases through significant weight loss, dietary changes, and exercise — meaning blood sugar returns to normal without medication. However, the underlying predisposition remains, and ongoing monitoring is necessary.
At what age should I start worrying about diabetes?
The ADA recommends screening starting at age 35 for all adults, regardless of symptoms. Earlier screening is warranted if you have risk factors: BMI over 25, family history of diabetes, history of gestational diabetes, polycystic ovary syndrome (PCOS), or if you belong to a high-risk ethnic group. Type 1 can develop at any age, so never dismiss classic symptoms — even in adults.
What to Do Next
The symptoms of diabetes — thirst, frequent urination, fatigue, blurry vision, slow-healing wounds — are your body’s way of signaling that blood sugar regulation has gone off track. Type 1 symptoms demand urgent attention within days. Type 2 symptoms are easier to dismiss, which is precisely why screening matters. If you have even one risk factor and haven’t been tested recently, schedule a fasting glucose or A1C test. Catching diabetes — or prediabetes — early gives you the widest range of treatment options and the best chance of avoiding serious complications down the road. Don’t wait for symptoms to make the decision for you.