Warning signs of diabetes

Type 2 diabetes has a feature that makes it hard to spot: it often progresses silently, without a clear-cut symptom, sometimes for years. Knowing the warning signs remains useful, though, because they do exist and deserve to be taken seriously.

The most characteristic signs

• Unusual, persistent thirst, along with a need to urinate more often, including at night — a direct consequence of the excess sugar in the blood that the body tries to eliminate through urine, causing greater fluid loss than normal
• Unusual fatigue, that isn't explained by activity level or sleep — partly linked to cells' inability to properly use glucose as an energy source, despite its abundant presence in the blood
• Blurred vision, linked to blood sugar swings that temporarily affect the lens, with excess sugar changing its shape and therefore its ability to focus properly

Signs more specific to type 2 diabetes

• Slower healing than usual, even for minor wounds, as excess sugar affects the blood circulation and immune function needed for normal healing
• Genital itching or recurring urinary or genital infections, as excess sugar promotes the growth of certain fungi and bacteria
• Numbness or tingling in the hands or feet, a sign of early nerve damage linked to prolonged excess sugar — a symptom that, when it appears, usually reflects a relatively long-standing progression of the disease

Why these signs are often overlooked

These symptoms generally set in gradually, which makes them easy to attribute to stress, general tiredness, or simply aging — rather than to a specific cause. This gradual onset largely explains why about a quarter of people with diabetes in France are still unaware of their diagnosis — a proportion very close to what's observed in the United States (about 22 to 25% according to the latest CDC data). Globally, the proportion is even higher: according to the International Diabetes Federation's (IDF) 2025 Atlas, more than 250 million of the 589 million adults with diabetes are unaware of their condition, or more than four in ten, with major gaps between high-income and low-income countries.

The special case of no symptoms at all

It's worth noting that a significant proportion of people with type 2 diabetes show, at the time of diagnosis, strictly none of the symptoms mentioned above — with the diagnosis made incidentally, during a blood test done for a completely different reason, or as part of routine screening. This reality reinforces the importance of proactive screening in people at risk, rather than waiting for symptoms that, for a non-negligible share of those affected, will simply never appear before more serious complications develop.

When diabetes is revealed by a complication

For some people, type 2 diabetes is only discovered when one of its complications appears, because it had been progressing silently for years. This happens more often than one might think. An eye exam at the ophthalmologist's can reveal small lesions on the retina. Hospitalization for a heart attack or stroke often comes with a blood test that reveals high blood sugar. A foot wound that won't heal, a lingering skin infection, or erectile dysfunction in men, linked to damage to blood vessels and nerves, can also lead to the diagnosis.

Other signs, without being symptoms of diabetes itself, reveal the underlying terrain that favors it. Dark, velvety patches in the folds of the neck or armpits, called acanthosis nigricans, reflect insulin resistance. Bleeding gums and severe gum disease are more common with diabetes, and the relationship appears to run both ways. A history of diabetes during pregnancy or giving birth to a baby weighing more than 4 kg (about 9 lbs) are also signals worth mentioning to a doctor: they clearly raise the risk of type 2 diabetes in the following years.

These situations show why one shouldn't wait for symptoms. The earlier the diagnosis, the easier it is to prevent these complications, which develop over years. Screening itself is simple: a fasting blood test, prescribed by a primary care doctor and covered by French national health insurance, is enough in most cases.

When to see a doctor

The presence of one or more of these signs, especially combined with known risk factors (excess weight, a sedentary lifestyle, family history, age over 45), warrants a visit for blood test screening (fasting blood sugar or HbA1c). There's no need to wait for symptoms to get screened: in France, this screening is recommended every 3 years starting at age 45 for people with risk factors, regardless of any symptom felt.

Getting an objective read on your risk before a blood test

A screening tool like the FINDRISC score lets you estimate your diabetes risk level from simple, already-known criteria (age, waist circumference, physical activity level, family history), without waiting for symptoms to appear or for a first blood panel — a useful first step before discussing it with a healthcare professional, particularly for people still hesitant to see a doctor in the absence of a symptom that feels concerning enough.

Signs that should never be ignored

While most of the signs mentioned above warrant a visit within a reasonable timeframe, certain more pronounced symptoms — rapid, unexplained weight loss, very heavy thirst and urination combined with significant fatigue, altered consciousness — can signal a more acute situation requiring prompt medical care, particularly in someone with already-known but poorly controlled diabetes. These situations are less common with type 2 diabetes than with type 1, but deserve to be known so they aren't minimized if they occur.

The role of loved ones in noticing changes

Because symptoms progress gradually, close family or friends sometimes notice changes before the person themselves — more pronounced fatigue, more frequent bathroom trips, unusual thirst during shared meals. These outside observations, while not medical, can be a useful trigger for encouraging a visit, particularly for people who might tend to minimize or not notice these gradual changes in themselves.

Why some signs go unnoticed in older people

In older people, certain classic diabetes symptoms (increased thirst, fatigue) can be harder to distinguish from other changes linked to aging itself, which sometimes delays diagnosis further in this age group — even though it is already the most at risk, given the rising prevalence of type 2 diabetes with age. This reality reinforces the value of systematic, regular screening, independent of whether any symptoms feel significant, particularly after age 45.

To estimate your own risk level, take the “Am I at risk of diabetes?” test.