Blood tests can be used to assess your general health, as well as help your doctor diagnose or monitor a range of conditions. Blood tests are generally accurate, but they're not perfect. This information helps you understand what is involved.

Before having a blood test

If you have been referred for blood tests, you might ask:

• Do I really need to have these blood tests?
• What are the risks?
• What happens if the tests aren't accurate?
• What happens if I don't do anything?
• How much will the tests cost?
• How will I get the results and when?

Some tests require preparation, such as:

• fasting (not eating for several hours beforehand)
• not having certain foods or drinks before the test
• changing how or when you take a medicine or supplement before the test
• having the test at a certain time

So, it's important to check with your doctor or the pathology collection centre whether you need to do anything special beforehand.

How and where can I get a blood test in Australia?

You'll usually need to go to a pathology collection centre.

Your doctor will recommend a pathology collection centre close by – the address will be on the request form that they give you.

Sometimes, your doctor will collect blood for testing in their clinic. Blood tests are also routinely done in hospitals.

How long does it take to get a blood test?

For most people, having blood taken is quick and easy.

Depending on when and where you go for your test, you may have a wait at the pathology collection centre.

What happens during a blood test?

Before having a blood test, you'll have your details checked.

The blood is usually taken from a vein in your arm. To take the blood, a tourniquet will be put around your arm and you may be asked to make a fist. A tourniquet is a band that stops or slows the flow of blood from your arm.

A needle will then be inserted into a vein in your arm.

A small amount of blood is collected and put into one or more tubes and sent to a pathology service for analysis.

After the needle is removed, you'll need to keep pressure on the site where the blood was taken for a short while. Try not to use that arm too much for the rest of the day.

Are there any risks or side effects from having a blood test?

It may hurt a little when the needle goes in and comes out of your vein. Having the tourniquet on your arm may also feel a little uncomfortable. For most people, it doesn't hurt too much.

The most common side effect from having a blood test is bruising.

Bruising

You might bleed and bruise at the site where the blood is taken. This is more common in people who have problems with blood clotting.

Try applying an ice pack to the area to relieve any bruising or pain.

Difficulty finding a vein

Taking blood can be more difficult in some people than in others. It may be due to the blood not flowing well during the test, or veins that are difficult to access.

You can try the following to help improve your blood flow before having a blood test.

• Make sure you have enough to eat and drink in the days leading up to your blood test.
• Keep warm before and during your blood test.
• Go for a short walk before your blood test to get your blood pumping.

You should always check with your doctor or the pathology testing centre first about anything you need to do to prepare for your blood test.

Feeling faint

Some people faint or feel like they may faint during or after a blood test. If you think this might happen, you should let the person taking your blood know beforehand. They may recommend you lie down while they do the blood test.

You should take your time in getting up after the test, and sit down for a while after your blood is taken. If you can, arrange for someone to help you get home or back to work.

What are the different types of blood tests?

There are many different types of blood tests. Your doctor may order more than one test at a time, so several tubes of blood may need to be collected.

Some common blood tests include:

• blood glucose test
• full blood count
• HbA1c test (for blood glucose control, usually in people with diabetes)
• hCG test – human chorionic gonadotropin test (pregnancy test)
• kidney function tests
• liver function tests
• prostate specific antigen (PSA) test

Blood test to check on your heart, blood vessels and blood clotting include:

• cardiac enzymes
• cholesterol and lipid tests
• D-dimer test
• international normalised ratio (INR) test

Blood tests to check for inflammation include:

• C-reactive protein (CRP) blood test
• erythrocyte sedimentation rate (ESR) test

Blood tests to check the levels of certain elements and vitamins in your blood include:

• calcium blood test
• folate test
• iron studies blood test
• magnesium blood test
• vitamin B12 test
• vitamin D test

Blood tests to check hormone levels include:

• oestrogen blood test
• testosterone blood test
• thyroid function tests

How long do blood test results take?

The results of most common blood tests are available within a day or 2. Some blood tests may take longer than this.

Ask your doctor when your results are likely to be ready and whether they will contact you about the result. They may recommend a follow-up appointment to discuss your results.

Getting your results

If you want to know the results of your blood test, make an appointment to see your doctor.

Some pathology services will send you a copy of your results if asked by your doctor.

What do my results mean?

To understand what your blood test results mean, you should talk to your doctor. A result that is normal for one person could be abnormal for another.

Blood test results only have meaning in the context of:

• the reason you had the test, your age and sex
• your overall health
• your lifestyle
• any treatments or medicines you are taking, including complementary medicines and supplements

Are the results always accurate?

Blood tests are generally accurate, but sometimes they can be wrong.

A blood test can:

• suggest something is abnormal when it isn't, which is known as a 'false positive'
• suggest something is normal when it isn't, which is known as a 'false negative'

Whatever the results, your doctor will consider all aspects of your health before talking to you about what they mean.

What do blood tests cost?

The costs of different blood tests varies. Medicare covers all or part of the cost of most blood tests. Many are bulk billed — this means that Medicare pays the full cost so you don't have to pay anything.

Your doctor should explain if there will be an out-of-pocket cost involved. You can also call the pathology collection centre (the number will be on your request form) to ask how much your tests will cost and how much Medicare covers.