Preparing for a blood test: fasting, water and your medicines

A little preparation helps your results reflect your health accurately — and saves you a repeat visit. Here’s what most patients ask us before a blood test.

Do I need to fast?

Only some tests need fasting. Tests such as fasting blood sugar and, in many cases, a lipid profile are usually done after an overnight fast of around 8–12 hours. Many others — like a CBC, thyroid profile or HbA1c — usually don’t need fasting. Because requirements vary, always confirm with the clinic or your doctor when you book.

Can I drink water?

Plain water is generally fine during a fast and makes it easier to draw blood. Avoid tea, coffee, juice, chewing gum and smoking until your sample is taken, unless you have been told otherwise.

What about my regular medicines?

Don’t stop or skip any medicine on your own. Some tests are timed around a dose, so ask your doctor whether to take your medicine before or after the sample.

Quick checklist

• Confirm whether your test needs fasting, and for how long
• Keep your prescription or doctor’s note handy
• Wear a top with sleeves that roll up easily
• Drink water unless advised otherwise
• Eat something light after the sample if you were fasting

This article is general health information and is not a substitute for advice from your doctor.