Can you have high blood sugar without symptoms?

Why feeling fine proves nothing

Symptoms depend on a threshold, not on harm. Thirst and frequent urination begin when glucose exceeds what the kidneys can reabsorb — around 180–200 mg/dL (10–11 mmol/L). Below that line you can be well above the healthy range and notice nothing at all.

The numbers make the point. Roughly 1 in 5 people with diabetes in the United States has not been diagnosed, and the great majority of the 98 million American adults with prediabetes are unaware of it. Those people are not ignoring symptoms. They mostly do not have any.

Two things that mask it further

Adaptation. People who have run high for a long time often feel normal at levels that would floor someone else. A reading of 250 mg/dL can produce no complaints at all in someone whose body has adjusted to it over years — and the same reading can be alarming in someone whose usual number is 95.

Symptoms that get attributed elsewhere. Fatigue gets put down to stress, parenting or perimenopause. Recurrent thrush gets treated as a standalone infection. Slow-healing cuts get blamed on age. Each has a plausible alternative explanation, so none of them prompts a glucose test on its own.

Screening is what catches it, not symptoms

Because you cannot feel the early stage, the only reliable route is testing. Current US guidance suggests screening all adults from age 35, and earlier if you carry additional risk: overweight or obesity, a first-degree relative with type 2 diabetes, a history of gestational diabetes, polycystic ovary syndrome, high blood pressure, or being of South Asian, Black, Hispanic, or Native American background.

A fasting glucose or an A1c is a single blood draw and is often already part of routine bloodwork. If you have not had one in three years and any of the above applies to you, that is a reasonable and specific thing to ask for at your next appointment.

The upside of catching it early is real: prediabetes is frequently reversible, and the interventions that work best are the ones started before symptoms ever arrive.