Fasting blood sugar (FBS) test
Quick answer: A fasting blood sugar test measures the glucose in your blood after you have not eaten for at least 8 hours; some options also check sugar in urine. Doctors order it to screen for and monitor diabetes and prediabetes.
- SampleBlood (and urine for one option)
- TakesAbout 5 minutes
- Before the testDo not eat or drink anything except water for 8 to 10 hours before the test.
- In fertility careHigh blood sugar before and during pregnancy affects mother and baby, so it is commonly checked before IVF and in pregnancy.
How the test is done
- 1You fast for 8 to 10 hours, usually overnight, drinking only water
- 2You come in the morning before eating
- 3A needle draws blood from a vein
- 4For the urine option, you also give a urine sample
What your results can mean
Reading your report
Fasting glucose limits are lower in pregnancy, so discuss your result with your doctor.
If the result is outside the usual range
A high level can be seen with diabetes, prediabetes, stress, illness or some medicines such as steroids. A low level can be seen with long fasting, some diabetes medicines or, rarely, hormone problems.
Who usually has this test
Adults having routine health checks, people at risk of diabetes, women with PCOS, and women before IVF or in pregnancy.
Risks and aftercare
Eat as soon as the sample is taken, especially if you take diabetes medicines.
Names and options
Also called: FBS, fasting glucose, fasting blood glucose
Options
- Blood only
- Blood with urine sugar
Listed by the hospital as
- FASTING BLOOD SUGAR
- FASTING BLOOD GLUCOSE WITH URINE
Questions about this test
Can I drink water before a fasting blood sugar test?
Yes, plain water is usually fine. Avoid tea, coffee, juice, milk and food for 8 to 10 hours. Ask your doctor whether to take your usual morning medicines.
Should I take my diabetes medicine before a fasting test?
Ask your doctor in advance. Some medicines can cause low sugar if taken without food, so your doctor will tell you what to do.
Why is fasting sugar checked before IVF?
High blood sugar can affect egg quality and early pregnancy. Finding and treating it beforehand helps protect you and the baby.
Related tests
Tamara Hospital & IVF Centre, Rajajinagar
34/3, 10th Cross Road, opp. Vardhaka Sardar Patel School, 1st N Block, 2nd Stage, Rajajinagar, Bengaluru 560010
The hospital is open 24 hours. Call before you come to check the timing for your scan or sample collection.
Get directions ↗IVF Pulse fertility care at Tamara Hospital →
Reception
Waiting area
IVF lab
This page explains each test in general terms so you know what to expect. It is not medical advice: your doctor decides which tests you need and what your results mean. Reference ranges differ between laboratories. Updated 4 November 2026.