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.
- 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 vascular disease.
- Glucose control:
- Other investigations similar to those for people with type 2 diabetes may be indicated.
Several cardiovascular findings are more prevalent, including hypertension, raised serum cholesterol, angina, abnormal heart findings and medical history of arteriosclerosis and stroke.
- Increasing evidence indicates that intervention can favourably influence the clinical course of impaired glucose tolerance, with some studies showing a 36% reduction in progression to diabetes.
- The metabolic syndrome (defined by impaired fasting glucose, large waist circumference, and high triglycerides) efficiently identifies subjects likely to have impaired glucose tolerance on oral glucose tolerance test, and thus be appropriate for diabetes prevention interventions.
- An overall assessment of cardiovascular risk is currently recommended.
- 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.
- Ongoing clinical trials are evaluating other agents, including angiotensin-converting enzyme (ACE) inhibitors, angiotensin receptor antagonists and thiazolidinediones, to prevent both type 2 diabetes and cardiovascular events. In combination with lifestyle modification, these therapies may provide effective prevention of type 2 diabetes and its consequences in high-risk patients.
- There has been some showing that ACE inhibitors may have a role in preventing diabetes, especially for those with other cardiovascular risk factors.
- 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 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)
- No authors listed; JBS 2: Joint British Societies' guidelines on prevention of cardiovascular disease in clinical practice. Heart. 2005 Dec;91 Suppl 5:v1-52
- 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.
- Lindstrom J, Ilanne-Parikka P, Peltonen M, et al; Sustained reduction in the incidence of type 2 diabetes by lifestyle intervention: follow-up of the Finnish Diabetes Prevention Study. Lancet. 2006 Nov 11;368(9548):1673-9.
- Meigs JB, Williams K, Sullivan LM, et al; Using metabolic syndrome traits for efficient detection of impaired glucose tolerance. Diabetes Care. 2004 Jun;27(6):1417-26.
- 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.
- Ratner R, Goldberg R, Haffner S, et al; Impact of intensive lifestyle and metformin therapy on cardiovascular disease risk factors in the diabetes prevention program. Diabetes Care. 2005 Apr;28(4):888-94.
- 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.
- Petersen JL, McGuire DK; Impaired glucose tolerance and impaired fasting glucose--a review of diagnosis, clinical implications and management. Diab Vasc Dis Res. 2005 Feb;2(1):9-15.
- Geng DF, Jin DM, Wu W, et al; Angiotensin converting enzyme inhibitors for prevention of new-onset type 2 diabetes mellitus: a meta-analysis of 72,128 patients. Int J Cardiol. 2013 Sep 10;167(6):2605-10. doi: 10.1016/j.ijcard.2012.06.125. Epub 2012 Jul 17.
- 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 Adrian Bonsall