What is Prediabetes?
Prediabetes means blood glucose is higher than normal but not yet high enough to be called diabetes — an A1C of 5.7-6.4% (39-46 mmol/mol), a fasting glucose of 100-125 mg/dL (5.6-6.9 mmol/L), or a two-hour glucose of 140-199 mg/dL (7.8-11.0 mmol/L). It usually causes no symptoms and is often reversible with changes to activity, eating, sleep, and weight.
Key takeaways
- Prediabetes is defined by specific lab ranges, not by symptoms — most people feel completely well.
- It is common: a large share of adults with prediabetes do not know they have it.
- Progression to type 2 diabetes is not inevitable; structured lifestyle programs cut that risk substantially.
- Prediabetes also signals higher cardiovascular risk, so blood pressure and cholesterol deserve attention too.
- Retesting is usually recommended at least yearly once prediabetes is identified.
Overview
Prediabetes is a warning light rather than a disease in the usual sense. Blood glucose has drifted above the normal range because tissues have become less responsive to insulin, but the pancreas is still keeping up well enough that the diabetes thresholds have not been crossed. Because there are almost never symptoms, it is nearly always found through a blood test ordered for screening or for something else entirely. That silence is precisely why routine screening from age 35 — or earlier for people with overweight plus another risk factor — matters.
The practical significance is twofold. First, without intervention a meaningful proportion of people with prediabetes go on to develop type 2 diabetes within several years. Second, the same metabolic changes that raise glucose also raise cardiovascular risk, so prediabetes travels with higher blood pressure, unfavourable cholesterol patterns, and fatty liver more often than chance would predict. The upside is that this is the stage where relatively modest changes produce the largest measurable payoff.
What Prediabetes is
Prediabetes is a laboratory category covering two overlapping states: impaired fasting glucose and impaired glucose tolerance. In impaired fasting glucose the liver releases slightly too much glucose overnight; in impaired glucose tolerance, muscle clears glucose too slowly after a meal. Some people have one, some have both, and A1C — which averages roughly three months of glucose exposure — can capture either.
It is best understood as a point on a continuous scale rather than a switch. Someone with an A1C of 5.8% (40 mmol/mol) is in a very different position from someone at 6.4% (46 mmol/mol), even though both carry the same label, and the number can move in either direction.
Common symptoms
Prediabetes typically produces no symptoms at all, which is why lab screening is the only reliable way to find it.
- No symptoms — the most common presentation by a wide margin
- Mild fatigue that is easy to attribute to something else
- Increased thirst — uncommon, and usually only at the upper end of the range
- Slightly more frequent urination
- Occasional blurred vision after high-carbohydrate meals
Less common symptoms
- Darkened, velvety skin at the neck or armpits (acanthosis nigricans) — associated with insulin resistance
- Skin tags in the same areas
Risk factors
- Overweight or obesity, particularly central weight — the strongest modifiable driver
- Physical inactivity — fewer than 3 days a week of activity is a recognised risk marker
- Age 35 and older — insulin sensitivity tends to decline with age
- A parent or sibling with type 2 diabetes — inherited beta-cell capacity matters
- Previous gestational diabetes — a marker of limited insulin reserve under stress
- Polycystic ovary syndrome — frequently accompanied by insulin resistance
- High blood pressure or low HDL cholesterol with high triglycerides — the same metabolic cluster
- Short sleep duration, shift work, or untreated sleep apnea — associated with impaired glucose handling
Causes
The underlying process is insulin resistance. Excess energy stored in liver and muscle cells — and particularly fat stored inside the abdomen and around organs — interferes with insulin signalling, so more insulin is required to move glucose out of the blood. Early on the pancreas compensates. Prediabetes appears when compensation begins to fall slightly short.
Genetics set the baseline. Some people can carry substantial excess weight without glucose rising, while others develop prediabetes at a modest body mass index, especially in some Asian populations where risk begins at lower BMI thresholds.
How it is diagnosed
Prediabetes is identified with the same blood tests used for diabetes, read against the intermediate ranges.
| Test or assessment | What it looks at |
|---|---|
| A1C | A result of 5.7-6.4% (39-46 mmol/mol) falls in the prediabetes range. It requires no fasting, which makes it convenient for screening. |
| Fasting plasma glucose | A result of 100-125 mg/dL (5.6-6.9 mmol/L) after at least 8 hours without food indicates impaired fasting glucose. |
| Oral glucose tolerance test | A two-hour value of 140-199 mg/dL (7.8-11.0 mmol/L) after a 75 g glucose drink indicates impaired glucose tolerance; it is the most sensitive of the three. |
| Cardiometabolic workup | A lipid panel, blood pressure measurement, waist circumference, and liver enzymes are commonly checked at the same time, since these travel together. |
Treatment overview
The centre of gravity for prediabetes is behaviour change supported by structure, with medication considered in selected higher-risk situations. Any medication decision, including whether one is appropriate at all, belongs with a prescriber.
Structured lifestyle change programs
Year-long coached programs modelled on the Diabetes Prevention Program combine eating changes, activity goals, and accountability. They have the strongest outcome evidence in this area.
Nutrition counselling
Work with a registered dietitian to shift the overall pattern rather than chase individual foods, with attention to refined carbohydrate, fibre, and portion size.
Physical activity programming
A combination of aerobic activity and resistance training improves insulin sensitivity, with benefits that appear before any weight change.
Weight management support
Ranges from behavioural programs to, in some higher-risk cases, medication or metabolic surgery for people who also have obesity.
Medication in selected cases
A biguanide is sometimes considered for higher-risk situations such as younger age with obesity or previous gestational diabetes. This is a shared decision, and it is not standard for everyone with prediabetes.
Cardiovascular risk review
Blood pressure, cholesterol, and smoking status are addressed alongside glucose because prediabetes raises vascular risk in its own right.
Lifestyle considerations
- Target a 5-7% reduction in body weight if you carry excess weight — this is the amount tied to the largest risk reductions in trials.
- Accumulate at least 150 minutes a week of moderate activity, such as brisk walking, spread across most days.
- Add two weekly resistance sessions; more muscle mass means more capacity to store glucose.
- Swap refined grains for intact whole grains and add beans, lentils, vegetables, and nuts for fibre.
- Cut sugar-sweetened drinks first — they deliver a fast glucose load with little satiety.
- Walk for 10-15 minutes after your largest meal to blunt the post-meal glucose rise.
- Aim for 7-9 hours of sleep and get loud snoring evaluated.
- Limit alcohol, and if you smoke, seek support to stop — smoking worsens insulin resistance.
Prevention
- Know your numbers: ask for an A1C or fasting glucose if you are 35 or older, or younger with overweight plus a risk factor.
- Keep waist circumference in check — central fat is more metabolically active than fat elsewhere.
- Stay active most days rather than doing a single long weekly session.
- Choose water, unsweetened coffee, or tea as default drinks.
- Treat sleep as a metabolic variable, not a luxury.
- After gestational diabetes, arrange glucose testing 4-12 weeks postpartum and then at least every 1-3 years.
Warning signs and when to get help
Signs that need emergency care
If you believe you are experiencing a medical emergency, call emergency services immediately (911 in the United States).
- Marked thirst and urination with vomiting, confusion, or drowsiness — call emergency services, as this suggests glucose has risen well beyond the prediabetes range
Signs that warrant a prompt appointment
These are not emergencies, but they are worth a call to your clinician rather than a wait-and-see.
- New persistent thirst, frequent urination, or unexplained weight loss
- Blurred vision that does not settle
- Numbness or tingling in the feet
- An A1C that has risen since your last test
Questions to ask a healthcare professional
Take these to your next appointment — or build an agenda with the Appointment Prep tool.
- What exactly were my A1C and fasting glucose numbers?
- How often should I be retested?
- Am I eligible for a recognised Diabetes Prevention Program near me or online?
- Should we also check my cholesterol, liver enzymes, and blood pressure?
- Is medication worth considering in my particular situation, and why or why not?
- What weight change would be realistic and useful for me?
- Could any of my current medicines be raising my blood sugar?
Frequently asked questions
Does prediabetes always turn into diabetes?
No. Without changes, a meaningful share of people progress over several years, but structured lifestyle programs cut that risk substantially, and some people return to normal glucose levels. Regular retesting is how you find out which way things are moving.
How long does it take to reverse prediabetes?
A1C reflects roughly three months of glucose exposure, so meaningful changes usually show up on a retest at three to six months. Fasting glucose can respond sooner. Consistency matters more than intensity in the first few weeks.
Do I need a glucose meter if I have prediabetes?
Usually not routinely. Most people are monitored with periodic lab tests rather than daily finger sticks. Some find short periods of self-monitoring or a continuous glucose sensor useful for learning how specific meals affect them — worth discussing with your clinician.
Is prediabetes dangerous on its own?
It carries higher cardiovascular risk than normal glucose, independent of whether it progresses to diabetes. That is why blood pressure and cholesterol are usually reviewed at the same time. Our heart health guide covers those levers.
Can I have prediabetes at a normal weight?
Yes. Genetics, muscle mass, fat distribution, sleep, and activity all contribute, and risk begins at lower BMI thresholds in some Asian populations. Weight is one input, not the whole picture.
Sources
- CDC — Prediabetes and the National DPP — Prevention program structure and eligibility
- NIDDK — Prediabetes and Insulin Resistance — Mechanism and testing explained in plain language
- American Diabetes Association — Diagnostic ranges and screening guidance
- USPSTF — Prediabetes and Type 2 Diabetes: Screening — Screening from age 35 in adults with overweight or obesity
Health Captain links to primary public-health and clinical sources so you can read the original material yourself. See our sources policy.