By Dr George Samra, MB, BS (Sydney), FACNEM

The correct test for Reactive Hypoglycemia is a G.T.T. The test should be ordered by the doctor as follows: G.T.T. – 4 hours. All 1/2 hourly readings. No special diet prior.

The Glucose Tolerance Test is the classical test used in diagnosing Diabetes. The Diabetic test is a 2 hour G.T.T. with just 3 readings, the fasting, the 1 hour and the 2 hour. This test is not correct for testing Functional or Reactive Hypoglycemia. With Hypoglycemia one is interested in the full reactions to a sugar load. In both cases a 75gram load of glucose is given to the patient after having collected blood for the fasting level. With Reactive Hypoglycemia the emphasis in on the word “Reactive”- one is looking for the sugar reactive phenomenon in which the blood sugar either drops suddenly or falls very low. Part of diagnostic criteria for Hypoglycemia is the rate of fall of blood sugars, hence the relationship between consecutive readings is very important. Sudden drops in blood glucose will usually trigger an adrenaline response and subsequently adrenaline symptoms such as nervousness, shakiness, dry mouth, irritability, agitation, neck stiffness and sometimes palpitations or a racy heart.

With Reactive Hypoglycemia one is also seeking to ascertain how low the blood sugar may go as this in fact is one of the measures of severity. The brain is dependent on blood glucose as it’s only fuel supply under normal circumstances. When the blood glucose falls below a certain level, usually 3.6mm/L, there is a lack of available fuel to the brain and symptoms of brain starvation will occur – these include tiredness, moodiness, depression, forgetfulness, poor concentration and cloudy headedness.

The purpose of the G.T.T is to clarify how well one tolerates glucose and by doing it properly one is able to see if the blood sugars drop too rapidly or fall too low. It is important that the glucose tolerance test is done accurately and properly. The following rules apply:

1.    Fasting for at least 10 hour prior. Usually this means fasting from 10.00p.m. the previous night.

2.    Once the fasting sugar level has been collected. A 75gm glucose load is given to the patient. In children this may be adjusted according to their size, however usually a 50gm glucose load is suitable for the vast majority of children.

3.    The pathology lab should be made aware that we are not trying to diagnose Diabetes but rather Reactive Functional Hypoglycemia. For this reason the doctor is requesting a longer test, i.e. 4 hours instead of 2 hours as well as all 1/2 hourly readings.

Does Insulin Need to be Measured?
Usually Insulin levels do not need to be measured. However, when the doctor suspects an Insulinoma (Cancer of the head of the Pancreas) and also in the case of an obese patient insulin levels may prove very useful in clarifying the diagnosis.

Determination of the Glucose Tolerance Test Results
The different types of Hypoglycemia have been classified based on the Glucose Tolerance Test. If the blood glucose levels falls below 3.6mm/L (65mg per 100ml) then Absolute Hypoglycemia is present. If the blood glucose level drops rapidly i.e., greater than 1.6mm/L (30mg per 100ml) in 1/2 an hour or greater than 2.6mm/L (50mg per 100ml) in 1 hour, then Relative Hypoglycemia exists. If the curve has a sharp gradient and numbers below 3.6mm/L together, then is regarded as the classical Reactive Hypoglycemia. The lower the blood sugar readings and the larger the gradient the blood glucose falls the more severe is the diagnosis. A fasting Hypoglycemia alerts the doctor the possible diagnosis of Insulinoma. The flat curve response and its implications have also been described elsewhere on this web site.

See results of a GTT and  here.

What to Say to Your Doctor & How to Approach Your Doctor
Most doctors have a problem understanding Reactive Hypoglycemia and this frustrates them. For this reason I’m including a letter to the doctor that you should download and which should help you get a satisfactory response from your doctor.

HYPOGLYCEMIC HEALTH ASSOCIATION
P.O. BOX 830 KOGARAH NSW 1485
Web Site http://www.hypoglycemia.asn.au

Dear Doctor,

Your patient has identified with the many symptoms suffered by patients with Reactive or Functional Hypoglycemia. As you well know, Hypoglycemia is low blood sugar, however Reactive Hypoglycemia is a sugar reactive phenomenon (and is not Diabetes.) After a sugar load such as a soft drink or cake, patients with this condition often suffer symptoms due to a sudden drop in their blood sugars, which typically occurs between 1 1/2 hours and 2 1/2 hours after the sugar consumption. Typical symptoms of Hypoglycemia include tiredness, poor concentration, moodiness, depression, forgetfulness, nervousness and irritability.

The brain relies on glucose as its only fuel under normal circumstances. The symptoms of Hypoglycemia relate to the fact that the brain is not being fueled properly at some point in time. In order to investigate this condition and help your patient please order a Glucose Tolerance Test as follows:
GTT 4 Hours. All 1/2 Hourly Readings. No Special Diet Prior.

This is the correct way to order a test for Reactive Hypoglycemia. The patient is usually given a 75gm load of glucose soon after the fasting level has been collected. With the prolonged GTT and with the 1/2 hourly readings one is able to ascertain both the rate of fall of blood sugars as well as whether they in fact fall below the Hypoglycemia line that is usually 3.6 mm/L (65mg per 100ml). Guidelines for interpretation of the Glucose Tolerance Test are available on the web site or directly from the Hypoglycemic Health Association.

Thank you sincerely for your co-operation. This test may help to clarify many troublesome symptoms that your patient has been experiencing.

Yours sincerely,
The Hypoglycemic Health Association.