Understand

Prediabetes: what your numbers mean

Prediabetes means blood sugar is above normal but below the diabetes thresholds: fasting 100–125 mg/dl, 140–199 two hours after a meal, or an A1C of 5.7–6.4 %. It is the one stage of glucose trouble with strong evidence that the trend can be turned around — which is exactly why it is worth taking seriously now.

The numbers that define it

The ADA draws the prediabetes bands one step below diabetes in each of the three tests:

• Fasting: 100–125 mg/dl (normal is 70–99; 126 and above is the diabetes range).
• Two hours after a meal: 140–199 mg/dl (normal is below 140; 200 and above is the diabetes range).
• A1C: 5.7–6.4 % (normal is below 5.7; 6.5 and above is the diabetes range).

Any one of the three can place you in the range, and a diagnosis requires a lab test confirmed on a second occasion — a single home-meter reading of 110 is a prompt to get tested, not a diagnosis. The full chart, with all three tests side by side, is in normal blood sugar levels.

What the diagnosis actually means

Prediabetes says the machinery that keeps glucose in range is under strain: the body still produces insulin, but cells respond to it less well, and the pancreas is compensating by working harder. Nothing has failed yet. Most people feel nothing at all — the numbers are usually the only symptom, which is why the diagnosis so often arrives as a surprise on a routine blood panel.

It is not a mild form of diabetes, and progression is not a scheduled event. Without any change, a meaningful share of people move on to type 2 diabetes over the following years — but a large share do not, and many move back to normal values. Which group you end up in is, to an unusual degree in medicine, influenced by what you do next.

The evidence: what the DPP showed

The Diabetes Prevention Program, a large US trial in people with prediabetes, tested a specific and unglamorous program: lose about 7 % of body weight and get at least 150 minutes of moderate activity per week — brisk walking counts. Compared with the control group, that program reduced progression to type 2 diabetes by 58 % over roughly three years. Participants over 60 did even better, at 71 %. A third group took metformin instead and reduced their risk by 31 % — effective, but roughly half the effect of the lifestyle arm.

Two things stand out in those results. The targets were modest — for a 200-lb person, 7 % is about 14 lb. And the benefit did not require reaching an ideal weight; the direction of travel mattered more than the destination.

What reversing it looks like in practice

• Weight, if there is weight to lose. Even 5 % moves fasting glucose measurably; 7 % was the DPP target. Crash diets are not required and rarely hold.
• Movement, most days. 150 minutes a week of anything brisk. Timing helps too — a short walk after meals blunts exactly the post-meal readings that define the 140–199 band.
• Food quality over food rules. Fewer refined carbohydrates and sugary drinks, more fiber, vegetables and protein — the specifics are in foods that steady your glucose and the broader ranking of interventions in how to lower blood sugar.
• Sleep. Short and irregular sleep worsens insulin resistance; it is the most commonly overlooked lever.

Occasional home measurements — a fasting value once or twice a week, logged with context in the journal — show whether the trend is moving, without turning life into a testing schedule. Remember the meter's ±15 % margin: watch the trend across weeks, not the difference between Tuesday and Wednesday.

Retesting: how often, which test

With a prediabetes diagnosis, the ADA advises retesting at least once a year — typically A1C or fasting glucose at the lab. Annual testing is frequent enough to catch progression early and infrequent enough to let changes show up: A1C reflects about three months of averages, so retesting a diet change after three weeks proves nothing. If results sit at the top of the range (fasting near 125, A1C at 6.3–6.4), your doctor may test sooner.

When metformin enters the conversation

Lifestyle change is the first-line answer, but not the only one. The ADA suggests considering metformin — a long-established, inexpensive diabetes medication — for people with prediabetes at higher risk of progressing: notably adults under 60, people with a BMI of 35 or above, and women who had gestational diabetes. In the DPP it cut progression risk by 31 %. It is an addition to lifestyle change, not a substitute, and the decision is individual — raise it with your doctor rather than waiting for it to be offered.

A reasonable plan for the next 12 months

1. Confirm the diagnosis with a lab test if it came from a home meter or a single result.
2. Pick the two levers you can sustain — for most people: a daily walk and cutting sugary drinks — rather than five you cannot.
3. Track weight monthly and a fasting reading weekly; look at the three-month trend.
4. Ask about metformin if you are in one of the higher-risk groups above.
5. Retest at the lab in 12 months — or sooner if your doctor says so — and recalibrate.

Prediabetes caught and acted on is, in many cases, a diagnosis you get to lose.