About 40 million Americans — roughly 1 in 8 people — have diabetes, and around 11 million of them (more than 1 in 4 of everyone affected) don’t know it yet, according to the CDC’s National Diabetes Statistics Report. On top of that, an estimated 1 in 3 U.S. adults has prediabetes, the metabolic precursor that often produces no symptoms at all. Recognizing the symptoms of diabetes early matters because timely treatment can prevent or delay the serious complications — nerve damage, kidney disease, vision loss, and cardiovascular disease — that uncontrolled blood sugar causes over time. This article is general information, not medical advice; only a clinician can diagnose diabetes.
Call 911 or go to the nearest emergency room now if you or someone else — especially a child, teen, or newly diagnosed person — has signs of diabetic ketoacidosis (DKA):
- Excessive thirst and frequent urination together with nausea, vomiting, or severe abdominal (belly) pain
- Breath that smells fruity or like nail-polish remover
- Rapid, deep, or labored breathing
- Confusion, extreme drowsiness, trouble staying awake, or fainting
- A very high blood glucose reading (often above 250–300 mg/dL) with any of the above
DKA is a life-threatening emergency that can develop within hours, most often in type 1 diabetes and sometimes as the first sign of it. A similar emergency in type 2 diabetes — very high blood sugar with severe dehydration, weakness, and confusion (hyperosmolar hyperglycemic state, or HHS) — also needs emergency care. Do not wait to see if symptoms improve.
The short version: The classic warning signs of diabetes are unusual thirst, urinating more than normal (including waking at night), losing weight without trying, constant hunger, fatigue, and blurry vision. In type 1 these appear quickly, often in kids and young adults; in type 2 they creep in over years and are easy to dismiss. Any of these signs deserves a prompt blood test — don’t wait. And the DKA red flags above are a 911 emergency.
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, including in older adults, where it is sometimes mistaken for type 2. 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, older age, 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. Increasingly, type 2 is also being diagnosed in children and adolescents, tracking with rising rates of childhood obesity.
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 a return of bedwetting in a previously dry child 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. It is the central 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.
Blurred Vision
High blood sugar draws fluid into the lens of the eye, changing its shape and affecting your ability to focus. Vision may be intermittently blurry and can shift from day to day. If caught early and blood sugar is brought under control, these vision changes usually reverse. Prolonged uncontrolled diabetes, however, can cause diabetic retinopathy — permanent damage to the retinal blood vessels and a leading cause of blindness.
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 genital itching in men), 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. A large share of people with diabetes develop some degree of neuropathy over time, per the NINDS.
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, and it is often seen in children and teens developing type 2.
Symptoms More Common in Type 1 Diabetes
Type 1 symptoms develop rapidly — over days to weeks — and tend to be more acute. Because they can escalate quickly into diabetic ketoacidosis, they should never be brushed off, particularly in a child or teen.
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 acids called ketones that make the blood dangerously acidic. DKA is more common in type 1 and is frequently the presenting problem at the very first diagnosis. In children, these symptoms are sometimes mistaken for a stomach bug or the flu, which can delay urgent care.
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 — see the emergency box at the top of this article.
Rapid, Deep Breathing
As ketones build up and the blood becomes acidic, the body tries to blow off excess acid by breathing rapidly and deeply (a pattern called Kussmaul respirations). Fast or labored breathing alongside the other DKA signs is a medical emergency.
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.
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, generally between weeks 24 and 28 of pregnancy. Risk factors include being older than 25, excess weight before pregnancy, family history of type 2 diabetes, and certain ethnic backgrounds (including Hispanic, Black, Native American, and 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, so follow-up glucose testing after pregnancy is important even when symptoms disappear.
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 considerably more likely to die from heart disease than adults without it, 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 (albuminuria) and eventually reducing kidney function. About 1 in 3 adults with diabetes has some degree of chronic kidney disease, per the NIDDK.
Diabetic Retinopathy
Elevated blood sugar damages the tiny blood vessels in the retina, leading to diabetic retinopathy — a leading cause of new blindness in working-age adults. Early stages produce no symptoms, which is why annual dilated eye exams are recommended for people with diabetes. Caught early, treatments such as laser therapy 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 a large share of non-traumatic lower-limb amputations in the U.S. 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 or higher 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% or higher 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 overweight or obesity, family history, or a history of gestational diabetes. Screening should be repeated at least every three years if results are normal, or more often if you have risk factors.
A Note on Home Glucose Monitors
Over-the-counter continuous glucose monitors (CGMs) — small sensors worn on the arm that you can now buy without a prescription — have become widely available and are marketed to people without diabetes who want to track their glucose trends. These devices can be informative, but they are not a substitute for a diagnostic blood test. If a monitor shows readings that seem high, or if you have symptoms, confirm the picture with your clinician and a standard A1C or fasting glucose test rather than self-diagnosing from a wearable.
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 more than 1 in 4 U.S. adults with diabetes 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, a substantial share of people with prediabetes go on to develop type 2 diabetes within a few years, per the CDC. Lifestyle changes — modest weight loss, regular physical activity, and dietary improvements — can significantly reduce that risk, and structured programs like the CDC’s National Diabetes Prevention Program are designed to help.
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 a normal range without glucose-lowering medication. However, the underlying predisposition remains, and ongoing monitoring is necessary because diabetes can return.
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: overweight or obesity, family history of diabetes, history of gestational diabetes, polycystic ovary syndrome (PCOS), or membership in a higher-risk ethnic group. Type 1 can develop at any age, so never dismiss classic symptoms — even in adults.
Are the symptoms of type 1 and type 2 diabetes the same?
They overlap heavily — thirst, frequent urination, fatigue, hunger, and blurred vision occur in both. The main difference is speed and severity: type 1 symptoms come on quickly and can escalate to DKA within days, while type 2 symptoms build slowly and may be mild for years. Any of them warrants testing, but the rapid, dramatic version — especially in a child, teen, or young adult — needs urgent evaluation.
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, and the DKA red flags in the box above are a call-911 emergency. 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.
Medical disclaimer: This article is for general educational purposes only and is not medical advice. It cannot diagnose diabetes or replace evaluation by a qualified clinician, and it does not provide dosing guidance for insulin or any other medication. If you have symptoms that concern you, contact your doctor. If you have any of the emergency red flags described above, call 911 or your local emergency number right away.
Sources
- Centers for Disease Control and Prevention (CDC) — National Diabetes Statistics Report
- National Institute of Diabetes and Digestive and Kidney Diseases (NIDDK) — Diabetes Symptoms & Causes; Chronic Kidney Disease
- Mayo Clinic — Type 1 Diabetes; Type 2 Diabetes: Symptoms and Causes; Diabetic Ketoacidosis
- American Diabetes Association (ADA) — Diagnosis and Screening
- American College of Obstetricians and Gynecologists (ACOG) — Gestational Diabetes
- National Institute of Neurological Disorders and Stroke (NINDS) — Peripheral Neuropathy
- American Heart Association — Diabetes and Cardiovascular Disease