At a glance
The HbA1c and Glucose Tolerance Test are blood tests used by endocrinologists (hormone and metabolism specialists) to measure how well the body is controlling blood sugar. The HbA1c test reads a molecule called glycated haemoglobin, which is haemoglobin (the protein in red blood cells that carries oxygen) that has glucose stuck to it. Because red blood cells live for about three months, this single reading tells the doctor what your average blood sugar has been over that whole period.
The Glucose Tolerance Test (often abbreviated GTT) works differently: you drink a measured sugar solution, and the lab checks your blood sugar at set intervals afterward. This shows whether your body releases enough insulin (the hormone that moves sugar out of the blood and into cells) and whether it does so quickly enough. Together, these two tests give a detailed picture of how the body handles glucose.
Medical Condition
Doctors order one or both of these tests when they need to diagnose diabetes or pre-diabetes, or when they need to track how well a known diabetic patient is being managed. The choice between the two tests often depends on the clinical question: HbA1c gives a longer-term average, while the GTT reveals how the body responds to sugar in real time.
- Suspected type 2 diabetes (where the body's cells stop responding normally to insulin)
- Suspected type 1 diabetes (where the immune system destroys the cells that make insulin)
- Pre-diabetes screening, including people with a family history of diabetes or who are overweight
- Gestational diabetes (high blood sugar that develops during pregnancy), where the GTT is the standard test
- Monitoring long-term blood sugar control in a patient already diagnosed with diabetes
- Polycystic ovary syndrome (PCOS), which is linked to insulin resistance
- Routine screening for people with high blood pressure, high cholesterol, or a sedentary lifestyle
These tests are not suitable for every patient. Your doctor will choose an alternative test in certain situations.
- HbA1c results can be misleading in people with certain blood conditions such as sickle-cell anaemia or thalassaemia, which affect the lifespan of red blood cells
- The GTT is usually avoided during acute illness because stress hormones temporarily raise blood sugar and make results unreliable
- Patients who have had part of their stomach or intestine removed may absorb the sugar solution abnormally, making the GTT difficult to interpret
Risks & Complications
Both tests are very low-risk blood tests, and serious complications are rare. The discomforts that do occur are minor and short-lived.
- Brief pain or stinging at the needle site during blood draw
- Small bruise under the skin where the needle was inserted, usually fading within a few days
- Lightheadedness or feeling faint, particularly if the patient is anxious or has not eaten
- Nausea after drinking the glucose solution used in the GTT, occasionally vomiting
- Temporary low blood sugar (hypoglycaemia) in the hours after the GTT in some patients who produce a very strong insulin response
Preparation & Procedure
Preparation differs between the two tests. For the HbA1c alone, no fasting is required because the result reflects a three-month average and a recent meal will not change it. For the GTT, or when HbA1c is combined with a fasting glucose check, you stop eating and drinking anything other than plain water for at least eight to ten hours before the appointment, usually from midnight the night before.
Some medications can affect blood sugar readings. Your prescribing doctor will review your current medicines before the test. Steroids, some blood pressure medicines, and certain psychiatric medications are among those known to influence results. Do not stop any prescribed medication without being told to do so by your doctor.
Smoking and strenuous exercise are usually asked to be avoided on the morning of a GTT, as both can shift blood sugar levels temporarily. If you are unwell with a fever or infection on the day of the test, let the clinic know, because the test may need to be rescheduled.
The following tests or checks are commonly done alongside or before these blood tests, depending on your clinical situation.
- Fasting blood glucose (a plain blood sugar reading taken after fasting)
- Lipid panel (a cholesterol and fat test, often ordered at the same visit)
- Kidney function tests, particularly in patients already known to have diabetes
- Blood pressure and weight measurement
- Urine test to check for glucose or protein in the urine
On the day of the test, the steps typically follow this order.
- You arrive at the lab or clinic, confirm you have fasted if required, and a nurse checks your weight, height, and blood pressure
- A small blood sample is taken from a vein in your arm to get the baseline (starting) reading
- If only HbA1c is requested, the appointment ends here and you may eat and drink normally
- For the GTT, you are given a glucose solution to drink, usually within five minutes
- You wait in the clinic, resting and avoiding physical activity
- Further blood samples are taken at timed intervals, typically at one hour and two hours after the drink, though the exact schedule varies by hospital protocol
- Once all samples are collected, you are free to eat and drink, and the results are usually sent to your doctor within one to two working days
Aftercare
Recovery after these blood tests is immediate for most people. You can eat, drink, and resume your normal day as soon as the samples are taken and the GTT waiting period is over. There is no wound care beyond pressing a small cotton swab on the needle site for a minute or two to stop any bleeding.
- If you feel dizzy or lightheaded after the GTT, sit or lie down and let the clinic staff know before leaving
- Eat a normal meal as soon as the test is complete, especially if you fasted beforehand
- Check the needle site for any unusual swelling or redness over the next day; a small bruise is normal but persistent swelling is not
- Wait for your doctor to contact you with the results rather than trying to interpret reference ranges on your own, since normal values can differ between laboratories
- If your results indicate pre-diabetes or diabetes, your doctor will schedule a follow-up appointment to discuss next steps, which may include further tests, a referral to a dietitian (a food and nutrition specialist), or the start of treatment
- If you are being monitored for existing diabetes, bring a log of your home blood sugar readings to your follow-up appointment to help your doctor see the full picture
Cost & What Determines It
The cost of HbA1c and Glucose Tolerance Testing varies widely depending on where the test is done, how it is ordered, and what is included alongside it. A test ordered as part of a full endocrinology consultation at a private hospital in a major city will be priced very differently from a standalone blood draw at a local clinic.
- Type of test ordered: HbA1c alone is a single analysis, while the GTT requires multiple blood draws and laboratory processing at each time point, raising the overall cost
- Number of blood draws in the GTT: some protocols require only two samples, others require three or more, and each sample adds to the laboratory fee
- Hospital class and country: a private international hospital in a regional medical hub charges more than a general hospital or stand-alone laboratory
- Whether the test is standalone or bundled into a diabetes screening package or a general health check
- Specialist consultation fee: if an endocrinologist orders and interprets the results as part of a clinic visit, this is usually billed separately from the laboratory fee
- Additional tests ordered at the same time, such as a lipid panel, kidney function tests, or urine analysis
- Urgency: same-day or urgent result processing usually carries a surcharge
Hospital packages for diabetes screening or annual health checks often bundle the blood draw, laboratory fees, and a nurse consultation together. The specialist's interpretation, any additional imaging, and follow-up appointments are usually billed separately. Ask the hospital or laboratory for an itemised price list before you commit.
BPJS Kesehatan does cover HbA1c and glucose testing when ordered through the referral system within Indonesia, but it does not cover any tests or consultations done abroad. Most Indonesian private health insurance policies also exclude overseas treatment. Patients who travel abroad for these tests typically pay out of pocket or hold a private international health insurance policy that explicitly covers outpatient diagnostics outside Indonesia. Requesting a written cost estimate from the hospital before you travel is the most reliable way to avoid unexpected bills.
Frequently Asked Questions
Does the HbA1c or glucose tolerance test hurt?
Neither test is painful beyond a brief sting from a blood draw needle. The HbA1c requires only one small blood sample, while the glucose tolerance test (a test that measures how your body handles sugar over time) involves two or three blood draws spaced an hour or two apart. Most people find the waiting between draws the hardest part, not the needle itself.
Do I need to fast before the test?
Preparation depends on which test your doctor orders. For an HbA1c, fasting is usually not required because it reflects your average blood sugar over the past two to three months. For a glucose tolerance test, you will typically be asked to fast for at least eight hours beforehand and to avoid heavy exercise and certain foods in the days leading up to it. Your referring doctor or the clinic will give you exact instructions.
How long does the test take and when will I get my results?
An HbA1c blood draw itself takes only a few minutes, while a glucose tolerance test usually takes two to three hours in the clinic because you must wait and have blood drawn at set intervals after drinking a sugar solution. HbA1c results are often ready the same day or within a day, and glucose tolerance results are usually available within one to two days, though timing varies by laboratory.
How much does an HbA1c or glucose tolerance test cost?
The price depends on which test is ordered, the class of hospital or clinic, and whether additional blood panels are run at the same time. A glucose tolerance test generally involves more blood draws and more laboratory work, so it tends to cost more than a standalone HbA1c. Requesting a written cost estimate directly from the hospital is the most reliable way to know what you will pay.
This page is general information, not a substitute for medical advice. Every case is different. Your doctor decides what is right for you.
