The only way to know for sure if you have diabetes is through a blood test, but your body often sends warning signs before you ever see a doctor. Frequent urination, unusual thirst, unexplained weight loss, and constant fatigue are the most common early symptoms. Some people, especially those developing type 2 diabetes, can have the condition for up to 10 years without knowing it because the symptoms creep in so gradually they’re easy to dismiss.
Symptoms That Should Get Your Attention
Type 1 and type 2 diabetes share a core set of symptoms: urinating frequently (especially at night), extreme thirst, feeling more tired than usual, losing weight without trying, blurred vision, increased hunger, and cuts or wounds that heal slowly. Genital itching or recurring yeast infections are another signal many people overlook.
The key difference is speed. Type 1 diabetes tends to announce itself quickly, sometimes over just a few weeks, and the symptoms are hard to ignore. Type 2 develops much more slowly. You might notice you’re a little more tired, a little thirstier, getting up once more at night to use the bathroom. Each change feels minor on its own, which is why so many people with type 2 diabetes go years without a diagnosis.
Physical Changes You Can See
Before blood sugar reaches diabetic levels, insulin resistance can leave visible marks on your skin. The most recognizable is a condition called acanthosis nigricans: patches of dark, velvety skin that typically appear on the back of the neck, in the armpits, or in the groin. These patches develop because excess insulin in the blood triggers skin cells to multiply faster than normal. They can start small enough that you’d only notice on close inspection, or they can spread across the entire neck and become visible from the front.
Skin tags are another physical clue. These small, soft, skin-colored growths tend to cluster on the neck, armpits, and groin. Having five or more skin tags in these areas is considered a marker of insulin resistance. In women, skin tags under the breasts carry the same association. Neither skin tags nor dark patches guarantee you have diabetes, but they’re a reason to get tested.
The Tests That Confirm a Diagnosis
Three blood tests are used to diagnose diabetes, and any one of them can give you an answer.
- A1C test: This measures your average blood sugar over the past two to three months. Below 5.7% is normal. Between 5.7% and 6.4% means prediabetes. At 6.5% or higher, you have diabetes.
- Fasting blood sugar test: You fast overnight, then have your blood drawn. A reading of 99 mg/dL or below is normal. Between 100 and 125 mg/dL is prediabetes. At 126 mg/dL or higher, you have diabetes.
- Oral glucose tolerance test: You drink a sugary solution, then have your blood drawn two hours later. This test is less commonly used for general screening but is standard during pregnancy.
Doctors typically confirm the result with a second test on a different day before making a formal diagnosis, unless your symptoms and blood sugar levels are both clearly elevated.
Home Tests vs. Lab Tests
You can buy A1C kits and glucose meters over the counter, and they’re useful for spotting a potential problem. But home glucose meters can give readings that are 10 to 15% higher or lower than your actual blood sugar level. Factors like expired test strips, improper technique, or even room temperature can throw off results. A reading that looks normal at home could actually be in the prediabetic range, and vice versa.
Lab tests use advanced equipment designed to minimize these errors, so a clinical result is far more reliable. If a home test gives you a concerning number, treat it as a reason to get lab work done rather than a final answer. And if a home test looks fine but you’re experiencing symptoms, get lab work done anyway.
Who Should Get Screened Without Symptoms
The U.S. Preventive Services Task Force recommends that adults aged 35 to 70 who are overweight or obese get screened for prediabetes and type 2 diabetes, even if they feel perfectly fine. If you’re Black, Hispanic, American Indian, Alaska Native, Native Hawaiian, or Pacific Islander, screening should start earlier because these populations develop diabetes at higher rates. Asian Americans should be screened at a lower weight threshold (a BMI of 23 rather than 25).
A family history of type 1 diabetes is also a reason to be tested. The American Diabetes Association now recommends antibody-based testing for people without symptoms who have a first-degree relative with type 1. If one antibody test comes back positive, a repeat test within three months confirms the result. The more types of antibodies detected, the higher the risk of eventually developing type 1 diabetes.
Screening During Pregnancy
Gestational diabetes develops during pregnancy and is screened for between 24 and 28 weeks. The process usually starts with a one-hour glucose challenge: you drink a sugary solution, and your blood is drawn an hour later. If that result is elevated, you’ll take a longer follow-up test, either a two-hour or three-hour version, to confirm. With the three-hour test, a fasting level of 95 mg/dL or above, or a two-hour reading of 155 mg/dL or above, would lead to a diagnosis.
Gestational diabetes usually resolves after delivery, but it significantly increases the risk of developing type 2 diabetes later in life. If you had gestational diabetes in a previous pregnancy, you should be screened for type 2 diabetes regularly going forward.
Type 1 vs. Type 2: How Doctors Tell the Difference
Once diabetes is confirmed, figuring out whether it’s type 1 or type 2 matters because the treatments are different. In many cases, the distinction is obvious from the person’s age, symptoms, and body type. But when the picture is unclear, doctors order antibody tests. The most commonly used is a test for anti-GAD antibodies, which has the highest accuracy for detecting type 1 diabetes in adults. Islet cell antibodies and insulin autoantibodies are also tested.
If these antibodies are present, the immune system is attacking the insulin-producing cells in the pancreas, which is the hallmark of type 1 diabetes. If no antibodies are found, the diagnosis is almost certainly type 2. This distinction is especially important for adults diagnosed later in life, since type 1 diabetes can develop at any age and is sometimes misdiagnosed as type 2.