PatientPlus articles are written by UK doctors and are based on research evidence, UK and European Guidelines. They are designed for health professionals to use, so you may find the language more technical than the condition leaflets.
- Impaired glucose tolerance is defined as a fasting plasma glucose concentration of less than 7.0 mmol/L with a two-hour oral glucose tolerance test value of 7.8 to 11.1 mmol/L.
- Impaired fasting glycaemia is defined as a fasting glucose of 6.1 to 6.9 mmol/L.
- The World Health Organization (WHO) has recommended that people with an HbA1c of 42−47 mmol/mol (6.0-6.5%) are at high risk of diabetes.
Impaired glucose tolerance, typically characterised by hyperglycaemia and insulin resistance, is considered to be a stage in the development of type 2 diabetes mellitus and a risk factor for cardiovascular disease. Therefore, impaired glucose tolerance is often referred to as pre-diabetes.
- The prevalence of impaired glucose tolerance increases linearly from about 15% in middle age to 35-40% in the elderly.
- Evidence suggests that a 1 kg/m2 increase in body mass index (BMI) increases the risk of developing new-onset type 2 diabetes by 8.4%. The risk of impaired fasting glucose rises by 9.5%.
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- A first-degree relative with diabetes.
- Ethnicity: South Asian, Chinese, African-Caribbean and black African.
- Increasing age.
- Level of deprivation in the area where someone lives.
- Patients with impaired glucose tolerance are usually asymptomatic.
- Features of related risk factors for cardiovascular disease may be present, even with a mild degree of hyperglycaemia. They include hypertension, obesity, dyslipidaemia and macrovascular disease, such as stroke, coronary disease or peripheral arterial disease.
- Glucose control:
- Fasting blood glucose.
- Glycosylated haemoglobin.
- Oral glucose tolerance test.
- Other investigations similar to those for people with type 2 diabetes may be indicated.
- It has been shown that the risk of progression from impaired glucose tolerance to type 2 diabetes mellitus can be reduced by lifestyle interventions.
- Several clinical trials have found that lifestyle modification is the most effective strategy to prevent progression to type 2 diabetes.
- The advice is essentially the same as diet and exercise advice in diabetes:
- Weight reduction, if appropriate.
- Reduction in total intake of fat and intake of saturated fat.
- Increasing intake of dietary fibre.
- Increasing physical activity.
The risk reduction of diabetes using metformin, pioglitazone, acarbose, valsartan and orlistat in clinical studies has ranged from 14% to 72%.
- Reversal of drug-related iatrogenic causation of glucose intolerance. Whenever possible, substitute agent(s) that do not have an adverse effect on glucose tolerance, or reduce the dosage of the offending drug - eg, replacing a thiazide diuretic when treating hypertension, minimising use of corticosteroids.
- Metformin should be considered for adults at high risk whose blood glucose measure (fasting plasma glucose or HbA1c) shows they are still progressing towards type 2 diabetes, despite their participation in an intensive lifestyle-change programme, or if they are unable to participate in lifestyle-change programmes because of a disability or for medical reasons.
- Orlistat should be considered for adults who have a BMI of 28.0 kg/m2 or more and whose blood glucose measure (fasting plasma glucose or HbA1c) shows they are still progressing towards type 2 diabetes, especially those who are not benefiting from lifestyle-change programmes, or who are unable to participate in physical activity because of a disability or for medical reasons.
- There has been some evidence that angiotensin-converting enzyme (ACE) inhibitors may have a role in preventing diabetes, especially for those with other cardiovascular risk factors.
National Institute for Health and Care Excellence (NICE) guidance
- High risk groups:
- People of South Asian, Chinese, African-Caribbean, black African and other high-risk black and minority ethnic groups.
- People with conditions that increase the risk of type 2 diabetes.
- High risk of type 2 diabetes (fasting blood glucose 5.5-6.9 mmol/L) or HbA1c 42-47 mmol/mol (6.0-6.4%):
- Offer an intensive lifestyle change programme to increase physical activity, to achieve and maintain weight loss and to increase dietary fibre and reduce fat intake, particularly saturated fat.
- Reassess weight and BMI and offer a blood test for fasting blood glucose or HbA1c at least once a year.
- Consider for adults at high risk whose blood glucose measurement (fasting plasma glucose or HbA1c) shows they are still progressing towards type 2 diabetes, despite their participation in an intensive lifestyle-change programme, or adults at high risk who are unable to participate in lifestyle-change programmes because of a disability or for medical reasons.
- Continue to offer advice on diet and physical activity along with support to achieve their lifestyle and weight-loss goals.
- Check the person's renal function before starting treatment, and then twice yearly (more often if they are older or if deterioration is suspected).
- Start with a low dose (for example, 500 mg once daily) and then increase gradually as tolerated, to 1500-2000 mg daily. If the person is intolerant of standard metformin, consider using modified-release metformin.
- Prescribe metformin for 6-12 months initially. Monitor the person's fasting plasma glucose or HbA1c levels at three-monthly intervals and stop the drug if no effect is seen.
- Orlistat should be considered for adults who have a BMI of 28.0 kg/m2 or more, whose blood glucose measurement (fasting plasma glucose or HbA1c) shows they are still progressing towards type 2 diabetes. In particular, this includes those who are not benefiting from lifestyle-change programmes, or who are unable to
participate in physical activity because of a disability or for medical reasons.
- Approximately 40-50% of individuals with impaired glucose tolerance will progress to type 2 diabetes over their lifetime.
- Impaired glucose tolerance is associated with an increased risk of cardiovascular disease.
- The precise relationship between impaired glucose tolerance and microvascular complications is less certain.
- Avoid being overweight and eat a healthy diet, with high fibre, low fat and lots of fruit and vegetables.
- Encourage regular physical activity.
Further reading & references
- Definition and Diagnosis of Diabetes Mellitus and Intermediate Hyperglycaemia; World Health Organization/International Diabetes Federation, 2006
- Type 2 diabetes prevention: population and community-level interventions; NICE Public Health Guidance (May 2011)
- Report of the Joint British Societies for the Prevention of Cardiovascular Disease; JBS3, 2014
- Ryden L, Grant PJ, Anker SD, et al; ESC Guidelines on diabetes, pre-diabetes, and cardiovascular diseases developed in collaboration with the EASD: the Task Force on diabetes, pre-diabetes, and cardiovascular diseases of the European Society of Cardiology (ESC) and developed in collaboration with the European Association for the Study of Diabetes (EASD). Eur Heart J. 2013 Oct;34(39):3035-87. doi: 10.1093/eurheartj/eht108. Epub 2013 Aug 30.
- Type 2 diabetes: prevention in people at high risk; NICE Public Health Guidance (July 2012)
- Roumen C, Feskens EJ, Corpeleijn E, et al; Predictors of lifestyle intervention outcome and dropout: the SLIM study. Eur J Clin Nutr. 2011 Oct;65(10):1141-7. doi: 10.1038/ejcn.2011.74. Epub 2011 May 18.
- Gillett M, Royle P, Snaith A, et al; Non-pharmacological interventions to reduce the risk of diabetes in people with impaired glucose regulation: a systematic review and economic evaluation. Health Technol Assess. 2012 Aug;16(33):1-236, iii-iv. doi: 10.3310/hta16330.
- Yates T, Haffner SM, Schulte PJ, et al; Association between change in daily ambulatory activity and cardiovascular events in people with impaired glucose tolerance (NAVIGATOR trial): a cohort analysis. Lancet. 2013 Dec 19. pii: S0140-6736(13)62061-9. doi: 10.1016/S0140-6736(13)62061-9.
- Smith-Marsh D; Pharmacological strategies for preventing type 2 diabetes in patients with impaired glucose tolerance. Drugs Today (Barc). 2013 Aug;49(8):499-507. doi: 10.1358/dot.2013.49.8.2002839.
- Geng DF, Jin DM, Wu W, et al; Angiotensin receptor blockers for prevention of new-onset type 2 diabetes: a meta-analysis of 59,862 patients. Int J Cardiol. 2012 Mar 8;155(2):236-42. doi: 10.1016/j.ijcard.2010.10.011. Epub 2010 Oct 30.
- DeFronzo RA, Abdul-Ghani M; Type 2 diabetes can be prevented with early pharmacological intervention. Diabetes Care. 2011 May;34 Suppl 2:S202-9. doi: 10.2337/dc11-s221.
- Sabanayagam C, Liew G, Tai ES, et al; Relationship between glycated haemoglobin and microvascular complications: is there a natural cut-off point for the diagnosis of diabetes? Diabetologia. 2009 Jul;52(7):1279-89. doi: 10.1007/s00125-009-1360-5. Epub 2009 Apr 22.
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Dr Colin Tidy
Dr Colin Tidy
Dr John Cox