Clinical biochemistry screens at Glasgow Hospital

Why might I need a clinical biochemistry screen?

Your doctor might request this screen if you have symptoms that could be linked to your liver, kidneys, thyroid or blood sugar, such as tiredness, dark urine, swelling or feeling unwell. It's also used more generally to investigate or monitor how your major organs, including your liver, kidneys, bones, are working, along with conditions such as diabetes and hormone problems.

Some tests within the screen, such as liver function tests, can also check whether a medicine you're taking is causing side effects.

What are the benefits of having one?

Generally, one specific single blood sample tube is needed to help check for a variety of different organs and conditions, your doctor will choose which the most relevant and appropriate test is for you. This includes checking how well treatment for a long-term condition is working, or whether a medicine is affecting your liver or kidneys, so your doctor can adjust it if needed.

Are there different types of biochemistry test?

Under the term of clinical biochemistry, these are common tests:

• kidney tests, sometimes called urea and electrolytes (U&Es), which check how well your kidneys are removing waste products and keeping your body's salts balanced
• liver tests (LFTs), which check for signs of liver damage or disease
• a bone profile, which measures calcium and phosphate, as changes in these can be linked to bone or kidney conditions
• a lipid profile, covering cholesterol, HDL ('good' cholesterol) and triglycerides, to help estimate your risk of heart disease
• thyroid function tests, which check for an overactive or underactive thyroid
• glucose and HbA1c, a marker that reflects your blood sugar over time, which screen for and help monitor diabetes.

Biochemistry laboratories can also test for other things when your doctor has a specific reason to, such as the levels of certain medicines in your blood, blood-forming nutrients like iron and vitamin B12, markers linked to some cancers, or more detailed hormone tests.

How do I prepare for a clinical biochemistry screen?

For most clinical biochemistry tests, you will not need to do anything special beforehand. Some parts of the screen, such as your cholesterol and triglyceride check, may need you to fast (avoid food and drink other than water) for a period before your appointment. Your doctor or the clinic will let you know if this applies to you.

What happens during the test?

Your doctor selects which specific tests you need from the screen on your request form. A venous blood sample is drawn from your elbow crease, using relevant blood sample tubes and sent to the laboratory for further analysis.

What happens after the test?

Depending on the laboratory and place, some results may be ready on the same day or a week later. Some of the more specialised tests take longer, and a small number are sent to other laboratories for specialist analysis, which can take several weeks.

Your results are sent to the doctor who requested the test, such as your GP or a hospital consultant, who will talk you through what they mean. A result outside the normal range does not automatically mean something is wrong. For example, a single high glucose reading is usually checked again before a diagnosis such as diabetes is confirmed.