Glucose tolerance test

 Glucose tolerance test 

A glucose tolerance test should be performed in the morning  after an overnight fast.

 It is important that the patient should  have had a normal diet for the preceding 3 days and should not  restrict carbohydrate intake drastically. 

The test should also not be  performed during an acute illness or following prolonged bedrest. 

  Plasma glucose concentrations are measured fasting and then  2 hours after a drink of 75 g of glucose in 250–350 ml of water  (in children: 1.75 g/kg up to maximum of 75 g).

 Several proprietary  preparations are available and these are often flavoured to make  items palatable.

 Table 1 shows normal values and interpretation  of abnormal values during an oral glucose tolerance test (OGTT).

  The role of oral glucose tolerance tests has changed given the  recent recommendations over the use of HbA1c as a preferred  means of diagnosing diabetes.

 Interpretation of the oral glucose  tolerance test results  Impaired fasting glycaemia (IGF)  Fasting glucose between 6.1 and 6.9 mmol/l in the absence of  abnormal values after the glucose load is defined as impaired  fasting glycaemia. 

Conversion to diabetes is not invariable but it is  important to reassess once a year, and in future this is likely to be  through HbA1c measurement (see Box 1.1). Individuals with IFG  should be advised about a healthy life-style and to avoid obesity.  Impaired glucose tolerance (IGT)  Once again conversion to diabetes is not invariable and patients  may either persist with impaired glucose tolerance, revert to normal  glucose tolerance or progress to type 2 diabetes. Obese individuals  should be advised to try and lose weight through diet and exercise.  The implications of this diagnosis for pregnancy are different.
.  IGF and IGT are collectively known asimpaired glucose regulation  but these terms may become outdated as HbA1c becomes the  recommended means of diagnosing diabetes and identifying those  at risk .
.  Diabetes mellitus
 A fasting glucose of greater than or equal to 7.0 mmol/l or a 2-hour  glucose value of greater than or equal to 11.1 mmol/l suggests 

Conversion Table for Blood Glucose Monitoring

People from outside the US may find this table convenient for converting US blood glucose values which are given in mg/dl into values generated by their blood glucose meters, which are generated in mmol/L.

mmol/L	mg/dl		mmol/L	mg/dl		mmol/L	mg/dl
0.06	1		6.7	120		16.0	288
0.28	5		7.0	126		16.6	300
0.55	10		7.2	130		17.0	306
1.0	18		7.5	135		18.0	325
1.5	27		7.8	140		19.0	342
2.0	36		8.0	145		20.0	360
2.2	40		8.3	150		20.8	375
2.5	45		8.9	160		22.2	400
2.8	50		9.0	162		23.0	414
3.0	54		9.4	170		24.0	432
3.3	60		10.0	180		25.0	450
3.9	70		10.5	190		26.4	475
4.0	72		11.0	196		27.7	500
4.4	80		11.1	200		30.0	540
4.7	85		12.0	216		33.3	600
5.0	90		12.5	225		38.8	700
5.5	100		13.9	250		40.0	720
6.0	106		14.4	260		44.4	800
6.1	110		15.0	270		50.0	900