Blood tests (venepuncture) — what to expect

Category: Biopsies, Lab & Pathology Tests · All biopsies, lab & pathology tests

What it is

A blood test draws blood from a vein, usually in the elbow crease, into labelled tubes for laboratory analysis — covering blood counts, kidney and liver chemistry, hormones, infections, immune markers and many more, depending on what your clinician requested.

Why it is done

Blood tests support diagnosis, monitoring of long-term conditions and medicines, screening, pre-operative assessment and checking treatment response. They are the most common medical test of all.

How to prepare

Some tests need fasting (you will be told — commonly for glucose and some lipid tests) or specific timing (for example drug levels, hormone tests). Drink water normally unless told otherwise — hydration makes veins easier. Tell the phlebotomist about fainting episodes, allergies and blood thinners.

What happens during the procedure

A cuff (tourniquet) is applied, the skin cleaned, and a fine needle or butterfly device enters the vein; several tubes may fill through the same puncture. It takes two to five minutes. You press on the site with cotton wool afterwards.

Afterwards — recovery & results

A small bruise is common; keep pressure for a few minutes and avoid heavy lifting with that arm briefly. Results return to the requesting team — timing varies from hours (urgent hospital tests) to one to two weeks for specialist assays. You will be told how results will reach you.

Risks & considerations

Risks are minimal: bruising, brief pain, and occasionally fainting — lie down for the test if you are prone to fainting and tell the team first. Infection is very rare with single-use equipment.

Watch: Blood tests (venepuncture) — what to expect videos

Real procedure videos from the MedicalVideos.com library. Some clinical footage is graphic — that is the nature of a medical video library.

▶ WatchBlood drawWatch on MedicalVideos.com ▶ WatchBlood test locate gene defects associated with cancerWatch on MedicalVideos.com ▶ WatchDraw blood sample venepunctureWatch on MedicalVideos.com

Related guides on MedicalVideos.com

Frequently asked questions

Why so many tubes?

Different tests need different preservatives and tube types, and some need larger volumes. One puncture fills them all.

Can I request my results directly?

In many systems you can view results through a patient portal or app once released. Ask your clinic how results are shared and what happens if something needs action.

Related procedures — Biopsies, Lab & Pathology Tests

Allergy testing (skin prick / specific IgE)Arterial blood gas (ABG) test Bone marrow biopsy Breast core biopsy Coagulation and thrombophilia tests Fine needle aspiration (FNA) cytology

Browse the B section of the A–Z list or return to the Procedures & Tests hub.

Please note: This page is educational information about a medical procedure or test. It does not replace the instructions of your own care team, who know your situation and whose preparation, fasting and medication advice you should follow if it differs from anything here. If you have symptoms that worry you, or an appointment you do not understand, contact your clinical team.