Undiagnosed Diabetes: Why You Won't Feel It Coming

You feel fine. You sleep, you work, you climb the stairs without thinking about it. So when a clinician suggests a blood sugar test, it is easy to wave it off. Nothing hurts, so nothing must be wrong.

That logic is exactly how undiagnosed diabetes hides. A new survey from the International Diabetes Federation found that 67% of at-risk adults wrongly believe pre-diabetes usually causes symptoms you would notice. Meanwhile, 252 million adults around the world have diabetes and do not know it.

This guide covers why the condition stays quiet, who should get screened and at what age, what each blood test number means, and how to get checked even if cost or time has stopped you before.

Why Undiagnosed Diabetes Feels Like Nothing at All

Most people picture diabetes as something you would feel: constant thirst, sudden weight loss, a trip to the emergency room. Those can happen. But the early stages often come with no symptoms at all, and that is the core message of the IDF's World Diabetes Day campaign this November.

The International Diabetes Federation's November 10 release describes a survey of 2,411 adults aged 25 to 64 in Brazil, India, Kenya, Saudi Arabia, Spain and the United States. Every respondent had known risk factors for type 2 diabetes. None had a diagnosis.

The results show a gap between knowing about diabetes and knowing your own risk:

• 84% agreed a risk check was worthwhile.
• Only 15% thought they personally were likely to develop type 2 diabetes.
• 43% said they would not feel confident arranging a check.
• In the US sample, just 13% recognised their personal likelihood.

IDF President Professor Schwarz put it plainly: "Awareness of diabetes is not the same as awareness of your own risk." The federation now asks health systems to correct "the belief that diabetes announces itself." One caveat: the survey samples were screened and unweighted, so they are not nationally representative. Treat the percentages as a signal about attitudes, not a census.

How Big the Diagnosis Gap Really Is

The global numbers are large enough to blur. So start with the totals, then shrink them to a scale you can picture.

The IDF's Diabetes Atlas puts the number of adults with diabetes at 589 million. Only about 57% know they have it. The World Health Organization has set a target of 80% diagnosed by 2030. Closing that gap would take roughly 134 million extra diagnoses, which the IDF works out to about 89,000 new diagnoses every single day until the end of 2030.

The US picture in one room

The CDC's national diabetes statistics count 40.1 million Americans with diabetes, about 12% of the population. Of those, 11.0 million are undiagnosed. That is 27.6% of adults with the condition.

Here is a quick way to make that real. Picture a waiting room with 100 adults who all have diabetes. About 28 of them have no idea. They are not on treatment, not watching their numbers, and not getting the eye, kidney or foot checks that diagnosed patients get.

Then add prediabetes. The CDC counts 115.2 million US adults in that range, where blood sugar is above normal but below the diabetes cutoff. Prediabetes is the stage where lifestyle changes have the most room to work, which is why finding it early matters so much.

Who Should Get a Diabetes Screening, and When

In the US, the main screening guideline comes from the US Preventive Services Task Force. It recommends screening adults aged 35 to 70 who have overweight or obesity and no symptoms, and gives that recommendation a grade of B.

Overweight means a body mass index (BMI) of 25 or more. Obesity starts at 30. If your first result is normal, the Task Force says rescreening every 3 years may be reasonable.

The guideline also tells clinicians to consider screening earlier for people with:

• A family history of diabetes
• A history of gestational diabetes (diabetes during pregnancy)
• Polycystic ovary syndrome (PCOS)
• American Indian or Alaska Native, Asian American, Black, Hispanic or Latino, or Native Hawaiian or Pacific Islander background

For Asian American patients, the Task Force notes that a lower BMI cut point of 23 may be appropriate. That detail matters, because many people assume a "normal looking" weight rules them out.

Run the numbers on your own BMI

The US formula is weight in pounds times 703, divided by height in inches squared. Two worked examples:

• A 40-year-old who is 5 feet 9 inches (69 inches) and 175 pounds: 175 × 703 = 123,025. Divide by 69 × 69 = 4,761. BMI is about 25.8. That is in the overweight range, so this person already falls inside the Task Force group.
• A 38-year-old Asian American who is 5 feet 6 inches (66 inches) and 145 pounds: 145 × 703 = 101,935. Divide by 66 × 66 = 4,356. BMI is about 23.4. Most charts call that normal, yet it clears the lower cut point of 23 the Task Force says may apply.

If you land in either group, bring it up at your next visit. If you are 35 and screened every 3 years until 70, that is up to 12 checks across those decades. Each one is a cheap chance to catch a slow change.

The Three Blood Tests and What Your Numbers Mean

The Task Force lists three tests clinicians can use: an A1C, a fasting plasma glucose test, or an oral glucose tolerance test. The CDC's diabetes testing guide gives the cutoffs for each.

A1C test

This reflects your average blood sugar over the past 2 to 3 months. You do not need to fast.

• Normal: below 5.7%
• Prediabetes: 5.7% to 6.4%
• Diabetes: 6.5% or above

Fasting blood sugar test

You fast overnight, then give a blood sample.

• Normal: 99 mg/dL or below
• Prediabetes: 100 to 125 mg/dL
• Diabetes: 126 mg/dL or above

Glucose tolerance test

You fast overnight, give a fasting sample, then drink a sugary liquid. Blood is checked at 1 and 2 hours, and sometimes at 3.

• Normal: 140 mg/dL or below at 2 hours
• Prediabetes: 140 to 199 mg/dL at 2 hours
• Diabetes: 200 mg/dL or above at 2 hours

Say your A1C comes back at 6.1%. That sits squarely in the prediabetes band, about halfway between the 5.7% and 6.5% lines. The CDC says people with prediabetes typically repeat the A1C every 1 to 2 years. Your clinician may also want a second test to confirm the result.

A1C is not perfect for everyone. The CDC lists conditions that can push it falsely high or low: severe anemia, kidney failure, liver disease, sickle cell anemia or thalassemia, some medicines including opioids and certain HIV drugs, recent blood loss or a transfusion, and early or late pregnancy. If any of those apply to you, tell the person ordering the test so they can pick the right one.

A smartwatch or a store-bought meter can make you curious, but it does not give you a diagnosis. Our guide to which fitness tracker numbers you can trust explains why consumer readings belong in a conversation with a clinician, not in place of one.

What Stops People From Testing, and How to Get Past It

The IDF survey asked people what held them back. The top answers were fear of the result (28%), cost (26%), trouble getting an appointment (20%) and lack of time (17%). In the US sample, 29% named cost.

Fear deserves a direct answer. A diagnosis does not change your blood sugar. It only changes whether you can do something about it. The IDF points to the UK Prospective Diabetes Study, where better glucose control after diagnosis cut small blood vessel complications by about a quarter, and heart attacks fell 15% over the following decade.

The practical barriers often have simple fixes:

1. Ask for an A1C with your next routine blood work. It needs no fasting, so it can ride along with tests you are already getting.
2. Ask about cost before the draw. Call your insurer or clinic and ask whether diabetes screening is covered for someone in your age and BMI group.
3. Look for walk-in checks. In the IDF survey, 46% said they would welcome checks at pharmacies or supermarkets, and many already offer them.
4. Book outside work hours. 38% of respondents wanted evening or weekend slots. Many clinics and labs have them if you ask.

If your result shows prediabetes or early type 2, you have options. A recent trial found that a structured diet and exercise plan put many younger adults into remission, which we cover in what the 54% diabetes remission result means. Regular resistance work helps too, and our piece on how much strength training you need each week lays out a realistic target. Any plan like this should be set up with your clinician, especially if you already take medication.

Frequently Asked Questions

Can you have diabetes and not know it?

Yes. The CDC estimates 11.0 million Americans have undiagnosed diabetes, about 27.6% of adults with the condition. Prediabetes and early type 2 diabetes often cause no symptoms, so a blood test is the only reliable way to find out.

At what age should I get screened for diabetes?

The US Preventive Services Task Force recommends screening adults aged 35 to 70 who have overweight or obesity. Clinicians may screen earlier if you have a family history, had gestational diabetes, have PCOS, or belong to a higher-risk ethnic group. Ask your clinician what fits your situation.

What A1C level means prediabetes?

According to the CDC, an A1C of 5.7% to 6.4% means prediabetes. Below 5.7% is normal, and 6.5% or above means diabetes. Your clinician interprets the result alongside your history and may repeat the test.

Do I need to fast for a diabetes blood test?

Not for an A1C test. You do need to fast overnight for a fasting blood sugar test and for a glucose tolerance test. Check with the lab or clinic when you book.

Get the Number, Then Decide

Undiagnosed diabetes stays hidden because it rarely hurts in the early years. The IDF survey shows most at-risk adults still expect warning signs that may never come, while hundreds of millions of people live with the condition unaware.

The fix is small. If you are 35 or older and carry extra weight, or you have a family history or another risk factor, ask your clinician for an A1C or fasting glucose test at your next visit. If the number is normal, you have peace of mind for a few years. If it is not, you have found it at the stage where you can still do the most about it.