How do I prepare for a blood test, and how do I read my report?

Medically reviewed by our consultant obstetrician & gynaecologist (MBBS, MS OBG). Last reviewed: 1 November 2026.

Which blood tests need fasting?

A few tests are affected by what you have just eaten. For these, you are usually asked to fast:

• Fasting blood sugar. Usually 8 to 12 hours without food.
• Lipid profile (cholesterol and triglycerides). Usually 8 to 12 hours without food. Some doctors accept a non-fasting lipid profile; follow what you are told.

Plain water is allowed and helps the sample be taken easily. Avoid tea, coffee, milk, juice, chewing gum and smoking until the sample is given. An easy way is to eat a light dinner, sleep, and give the sample early the next morning.

If you have diabetes and take tablets or insulin, ask the doctor before fasting. Skipping food on these medicines can make your sugar drop too low.

Which tests do not need fasting?

Most other blood tests can be done at any time of day, after a normal meal. This usually includes:

• Complete blood count (haemoglobin, white cells, platelets).
• Thyroid tests.
• Most hormone tests.
• Blood group and many infection screening tests.

If one fasting test is ordered along with others, it is simplest to give all the samples together on an empty stomach.

Do some tests need a particular day or time?

Yes. Some hormone tests are timed to a certain day of the menstrual cycle, counted from the first day of your period. Others are done in the morning, because the hormone level changes through the day. The doctor will tell you which day or time is right for your test. If you are not sure, ask before you go, so the test does not have to be repeated.

If you are planning a pregnancy or fertility treatment, read tests before IUI.

Should I stop my medicines before a blood test?

Usually not. Keep taking your regular medicines unless the doctor tells you to stop or delay a dose. Do not stop a medicine on your own.

Tell the lab staff and the doctor about everything you take, especially:

• Thyroid tablets. The doctor may ask you to give the sample before your morning dose.
• Biotin, or hair, skin and nail supplements that contain it. Biotin can change some hormone and thyroid results. The doctor may ask you to pause it for a short time before the test.
• Medicines for diabetes, blood thinners and any hormone tablets.

What should I bring for a blood test?

• The doctor's prescription or the list of tests.
• Your old reports, so the doctor can compare and see the trend.
• A list of the medicines and supplements you take.
• Something light to eat and drink after a fasting test.

Wear loose sleeves that roll up easily. Tell the staff if you have fainted during a blood test before, so you can lie down.

How do I give a good urine sample?

• Use the clean, closed container given by the lab. Do not touch the inside of the container or the lid.
• Wash your hands and wash the private area with plain water.
• Pass the first part of the urine into the toilet, then collect the middle part (midstream) in the container, then finish in the toilet.
• Close the lid tightly and hand it in soon.
• If the doctor asks for a first morning sample, collect the first urine you pass after waking up.

Tell the staff if you are having your period, as it can affect some urine results.

How do I read my blood test report?

Most reports are set out in the same way. Each line usually shows:

• Test name. What was measured, for example haemoglobin or blood sugar.
• Your value (result). The number found in your sample.
• Unit. How the value is measured. The same test can be reported in different units by different labs.
• Reference range. The range printed on your report, seen in most healthy people for that test.
• Flag. Many reports mark a value with H (higher than the range) or L (lower than the range), or print it in bold.

Reference ranges are printed on your report and vary between laboratories. They also differ with age, sex and pregnancy. So always compare your value with the range on the same report, not with a range from another lab or from the internet.

Is a value outside the range always a problem?

No. A reference range covers most healthy people, so some healthy people fall a little outside it. A value can also shift with a recent meal, a late night, an illness, exercise, your period or a medicine. One value slightly outside the range is often not a problem on its own.

The doctor reads your report together with your symptoms, your examination and your other results. Sometimes the test is simply repeated after a while. Please do not start or stop any medicine based on the report alone.

Are blood tests read differently in pregnancy?

Yes. In pregnancy the body changes, and the expected values for some tests, such as haemoglobin and thyroid tests, are different. The doctor uses ranges suited to pregnancy. Read about the first antenatal visit and thyroid problems in pregnancy.

Where can I get blood tests done and explained in Vasco, Goa?

Pai Hospital, Vaddem, Vasco-da-Gama has its own laboratory for routine blood, urine and hormone tests. Your report is explained by the Pai Hospital Team at your visit (see gynaecologist in Vasco). If you have old reports, send them by WhatsApp before your visit. Directions are on our contact page.

See all our services in Goa.

Or call +91 95459 20817 · +91 75582 52088 · 0832 251 3641

This page is for general education and is not personal medical advice. Treatment depends on your own examination and reports, so please speak to a doctor about your situation. We do not carry out or offer sex determination of any kind.