How often should I be retested?

With prediabetes, at least once a year is usual, or sooner if your weight or treatment changes significantly. The doctor adjusts this to your risk.

Can follow-up be done online?

Yes. The consultation and reviews are by video call anywhere in Spain, in English or Spanish, and blood tests are done at a lab near you. You can also be seen at the clinic in Fuengirola.

Journal Metabolic and weight

Prediabetes and insulin resistance: what to do next to turn it around

The glucose and HbA1c numbers that define prediabetes in mg/dL, mmol/L and mmol/mol, what insulin resistance is, and what really cuts diabetes risk.

5 min readEducational content by RejuvelookUpdated in October 2026

In short

Prediabetes means blood sugar above normal but below diabetes. The American criteria are a fasting glucose of 100 to 125 mg/dL (5.6 to 6.9 mmol/L) or HbA1c of 5.7 to 6.4%; the UK uses 42 to 47 mmol/mol. It has no symptoms but raises the risk of type 2 diabetes, and weight loss with activity roughly halves that risk.

Key points

The ADA defines prediabetes as fasting glucose of 5.6 to 6.9 mmol/L, HbA1c of 39 to 46 mmol/mol (5.7 to 6.4%), or 7.8 to 11.0 mmol/L two hours after a glucose drink.
Each year 5 to 10% of people with prediabetes develop diabetes, and a similar proportion return to normal.
A lifestyle programme cut diabetes risk by 58%, and the benefit was still 34% ten years later.
Every kilo lost was linked to a 16% lower risk of diabetes.
Insulin resistance is not diagnosed from a single index: the criteria rest on glucose and HbA1c.

Prediabetes is common, silent and, to a large extent, reversible. Knowing what your numbers mean, which ones matter and what has been shown to work lets you act with judgement rather than worry. If you have results from both Spain and home, this guide also explains why they may look different.

What prediabetes and insulin resistance are

Prediabetes is a state in which blood sugar is higher than normal but below the threshold for diabetes. It is not a disease in itself but a high-risk state: insulin resistance and early failure of the insulin-producing cells are both present, and both begin before glucose changes can be detected ^[3].

Insulin resistance means your cells respond less well to that hormone. The pancreas compensates by making more, and for years glucose stays close to normal. When it can no longer keep up, glucose rises. Excess abdominal fat, inactivity and genetics are the main drivers.

The numbers that define prediabetes

The American Diabetes Association (ADA) defines prediabetes as any one of the following ^[1]:

Fasting glucose of 100 to 125 mg/dL (5.6 to 6.9 mmol/L).
HbA1c of 5.7 to 6.4% (39 to 46 mmol/mol).
Glucose two hours after a glucose drink of 140 to 199 mg/dL (7.8 to 11.0 mmol/L).

Diabetes starts at 126 mg/dL (7.0 mmol/L) fasting, an HbA1c of 6.5% (48 mmol/mol) or 200 mg/dL (11.1 mmol/L) after the glucose drink ^[1].

Not every organisation draws the line in the same place. The WHO sets impaired fasting glucose from 6.1 mmol/L (110 mg/dL), and NICE in the UK uses an HbA1c of 42 to 47 mmol/mol (6.0 to 6.4%) ^[2]. Spanish labs usually report glucose in mg/dL and HbA1c as a percentage, so the same result can look different, and even carry a different label, depending on where it was taken.

The ADA recommends testing all adults from the age of 35, and earlier for people with overweight and other risk factors ^[1].

What about HOMA-IR? It estimates insulin resistance from fasting glucose and insulin. It is useful in research, but it is not part of the diagnostic criteria and has no accepted clinical cut-off ^[1].

How big the risk really is

Each year, 5 to 10% of people with prediabetes develop type 2 diabetes, and a similar proportion return to normal ^[3]. In a Cochrane review, between 33 and 59% returned to normal values within one to five years ^[4]. Nothing is set in stone.

Prediabetes is also linked to a slightly higher cardiovascular risk. A meta-analysis of 53 studies and over 1.6 million people put the increase at 13 to 30%, depending on the definition used ^[2]. It is a moderate risk, but it adds to blood pressure, cholesterol and smoking.

What has been proven to work

The evidence here is strong. In the Finnish Diabetes Prevention Study, a lifestyle programme cut the risk of type 2 diabetes by 58% ^[5]. In the large US Diabetes Prevention Program, lifestyle change achieved the same 58%, against 31% with the medication studied. Ten years on, the lifestyle benefit was still 34% ^[6].

Weight was the main driver: every kilo lost was linked to a 16% lower risk ^[7]. Current ADA recommendations propose losing at least 7% of body weight and doing 150 minutes of moderate activity a week, through a structured programme ^[8].

In practice, what works is:

Losing weight and keeping it off, even modestly.
Moving every day and adding strength exercise, which helps muscles take up glucose.
Eating mostly minimally processed food, with fewer sugary drinks.
Sleeping enough and not smoking.

If you are also carrying extra weight, our guide to medical weight loss in Spain explains how that is approached.

What the evidence says

Each statement shows its level of evidence and the sources behind it.

Supported

Prediabetes is diagnosed with fasting glucose, HbA1c or an oral glucose tolerance test, using thresholds set out in the guidelines.^[1]^[2]High-quality evidence
Lifestyle programmes combining weight loss and physical activity reduce progression to type 2 diabetes, and the benefit lasts for years.^[5]^[6]^[7]^[8]High-quality evidence

With caveats

Prediabetes is linked to a modestly higher cardiovascular risk, especially with the stricter definitions.^[2]Moderate evidence
A large share of people with prediabetes return to normal values, even without specific treatment, so results should be confirmed and monitored rather than feared.^[3]^[4]Moderate evidence

Not enough support

Insulin resistance indices such as HOMA-IR to diagnose or guide treatment: useful in research, with no accepted clinical cut-off.Low-quality evidence

What to expect, realistically

HbA1c reflects your average over two to three months, so changes are judged over that timescale, not in days. Returning to normal values is possible and common ^[4], but it does not last if the habits go.

The long-term follow-up of the large US trial shows this clearly: the lifestyle group regained some weight over the years and its advantage narrowed, although it did not disappear ^[6]. That is why follow-up continues, less often, once the goal is reached. What matters most in the long run is keeping the weight off ^[7].

The risk of doing nothing (and of doing too much)

Ignoring prediabetes lets a process continue that can often be stopped. The opposite extreme does not help either: crash diets, unproven supplements or anxiety over every glucose spike. People with prediabetes move between states for years, so it pays to confirm before acting ^[4].

If prediabetes comes with a large waist, raised blood pressure or high triglycerides, you may be looking at metabolic syndrome, which calls for a joined-up view.

How it works at Rejuvelook

Prediabetes and insulin resistance are managed within our weight and metabolic health programme, online anywhere in Spain and in person in Fuengirola, in English or Spanish. It starts with a medical video consultation. If needed, the doctor requests blood tests at a lab near you in Spain.

With your results, the doctor estimates your risk and proposes a staged plan built around weight, activity and food, with measurable goals: glucose, HbA1c, waist and body composition. Reviews are regular, and your reports are available in English to share with your GP at home. If medication becomes appropriate at any point, it is assessed individually and monitored.

When to see a doctor

Book a medical consultation, or go to A&E if it is severe or sudden, if you notice:

Strong thirst, passing a lot of urine, unexplained weight loss or blurred vision: these can mean diabetes is already present, so get a blood test soon.
A very high reading on a home meter together with feeling unwell, vomiting or drowsiness: go to A&E (urgencias).
You had diabetes in pregnancy: your risk is higher and worth checking regularly.
You are over 35 and have never had your glucose or HbA1c checked.

Frequently asked

Do I need to fast for the blood test?

For fasting glucose, yes: about eight hours without food. HbA1c does not need fasting, because it reflects your average over the previous two to three months. The doctor will tell you which tests make sense for you.

My UK result says HbA1c 44 mmol/mol, but the Spanish lab gives a percentage. How do they compare?

They measure the same thing in different units. 42 to 47 mmol/mol is roughly 6.0 to 6.4%, and 39 mmol/mol is about 5.7%. Bring both reports and the doctor will put them side by side.

I had one high reading. Do I have prediabetes?

Not necessarily. A single result is confirmed with a repeat test, or a different test, before any label is applied. Day-to-day variation is normal.

Should I wear a continuous glucose monitor?

It can help you see how your body handles certain meals, but it does not replace diagnostic tests. Isolated sensor readings should not lead to drastic changes without medical interpretation.

References

Sources checked against PubMed or Crossref. Cited as plain text, without links.

1.American Diabetes Association Professional Practice Committee. 2. Diagnosis and Classification of Diabetes: Standards of Care in Diabetes-2026. Diabetes Care. 2026;49(Supplement_1):S27-S49. doi: 10.2337/dc26-S002. PMID: 41358893.Verified on 2 October 2026
2.Huang Y, Cai X, Mai W, Li M, Hu Y. Association between prediabetes and risk of cardiovascular disease and all cause mortality: systematic review and meta-analysis. BMJ. 2016;355:i5953. doi: 10.1136/bmj.i5953. PMID: 27881363.Verified on 2 October 2026
3.Tabák AG, Herder C, Rathmann W, Brunner EJ, Kivimäki M. Prediabetes: a high-risk state for diabetes development. Lancet. 2012;379(9833):2279-90. doi: 10.1016/S0140-6736(12)60283-9. PMID: 22683128.Verified on 2 October 2026
4.Richter B, Hemmingsen B, Metzendorf MI, Takwoingi Y. Development of type 2 diabetes mellitus in people with intermediate hyperglycaemia. Cochrane Database Syst Rev. 2018;10(10):CD012661. doi: 10.1002/14651858.CD012661.pub2. PMID: 30371961.Verified on 2 October 2026
5.Tuomilehto J, Lindström J, Eriksson JG, Valle TT, Hämäläinen H, Ilanne-Parikka P, et al. Prevention of type 2 diabetes mellitus by changes in lifestyle among subjects with impaired glucose tolerance. N Engl J Med. 2001;344(18):1343-50. doi: 10.1056/NEJM200105033441801. PMID: 11333990.Verified on 2 October 2026
6.Knowler WC, Fowler SE, Hamman RF, Christophi CA, Hoffman HJ, Brenneman AT, et al. 10-year follow-up of diabetes incidence and weight loss in the Diabetes Prevention Program Outcomes Study. Lancet. 2009;374(9702):1677-86. doi: 10.1016/S0140-6736(09)61457-4. PMID: 19878986.Verified on 2 October 2026
7.Hamman RF, Wing RR, Edelstein SL, Lachin JM, Bray GA, Delahanty L, et al. Effect of weight loss with lifestyle intervention on risk of diabetes. Diabetes Care. 2006;29(9):2102-7. doi: 10.2337/dc06-0560. PMID: 16936160.Verified on 2 October 2026
8.American Diabetes Association Professional Practice Committee. 3. Prevention or Delay of Diabetes and Associated Comorbidities: Standards of Care in Diabetes-2026. Diabetes Care. 2026;49(Supplement_1):S50-S60. doi: 10.2337/dc26-S003. PMID: 41358891.Verified on 2 October 2026

Educational content. It does not replace a medical consultation or provide a diagnosis. Tests and treatments are indicated only after medical consultation and in line with regulation.