What is Chemical Chemistry?
Clinical chemistry is the analysis of fluids that come from inside the body, including blood, urine, saliva, mucus and other body fluids and tissues. By measuring the levels of different substances in these samples, doctors can detect disease, tell different conditions apart, check how organs such as the liver, kidneys and heart are working, and monitor treatment.
Our laboratory produces test results for a wide spectrum of diagnoses. Most of the testing is done on a small sample of blood or urine, which is collected from you and then analysed by trained laboratory staff using specialised equipment.
Clinical chemistry tests are used to:
- Screen for diseases before symptoms appear, such as diabetes and high cholesterol
- Help find the cause of symptoms such as tiredness, weight changes, thirst, swelling or pain
- Confirm or rule out a diagnosis
- Monitor a long-term condition, and see whether a treatment is working
- Check that a medicine is at a safe and effective level in your body
- Check that you are fit for a surgery or procedure
What Chemical Chemistry tests are available?
Routine biochemistry tests
These are the most commonly requested tests, and they cover many areas of health:
- Anaemia tests: Check for low red blood cells or haemoglobin and look for causes, such as low iron or vitamin levels
- Blood tests: Measure the levels of salts such as sodium and potassium, and other substances in your blood, that need to be kept in balance for your body to work properly
- Bone status: Measure calcium, phosphate, vitamin D and other substances that affect bone health
- Cardiac tests: Measure markers that are released when the heart muscle is under stress or damaged, which help doctors assess chest pain and heart conditions
- Blood gases: Measure oxygen, carbon dioxide and the acid-base balance of your blood, to see how well your lungs and kidneys are working. These are often needed in emergencies or for patients who are seriously ill
- Lipids: Measure cholesterol and triglycerides to assess your risk of heart disease and stroke
- Liver tests: Measure enzymes and other substances to check how well your liver is working
- Renal (kidney) tests: Measure waste products such as creatinine and urea to assess how well your kidneys are filtering your blood
- Urine chemistries: Analyse the chemicals in your urine, which can show problems with the kidneys, the urinary tract or blood sugar control
Therapeutic Drug Monitoring (TDM)
Some medicines need to be kept within a narrow range in your blood to work properly and to avoid side effects. Therapeutic drug monitoring measures the level of such a medicine in your blood, so that your doctor can adjust your dose if needed.
Endocrinology Tests
Endocrinology is the study of hormones, the chemical messengers that control many functions in the body. These tests include:
- Diabetes tests: such as blood glucose and HbA1c (the average blood sugar over the past two to three months)
- Thyroid tests: to check whether the thyroid gland is underactive or overactive
- Reproductive hormones: such as oestrogen, progesterone, testosterone and others, which can help to investigate fertility problems, menstrual problems and menopause
Tumor markers
Tumor markers are substances in the blood or other fluids that may be raised in some cancers. They are generally used to help monitor treatment, or to detect a return of a cancer that has been treated, rather than to diagnose cancer on their own. An example is the prostate-specific antigen (PSA) test, which is used in the assessment of prostate conditions.
Infectious serology
Serology tests look for antibodies or other markers in the blood that show whether you have been infected with, or are immune to, a particular infection, such as hepatitis B. They are often used for screening and to check immunity.
Why You Might Need These Tests?
Your doctor may order clinical chemistry tests as part of a health screening, or to look into symptoms, to monitor a condition you already have, or before a procedure. Different tests are linked to different conditions. For example:
- Prostate cancer: PSA and other tests may be used as part of the assessment and follow-up
- Urinary tract infection (UTI): urine tests can show signs of infection, such as white blood cells and bacteria, and may be used alongside a urine culture
- Women’s health conditions such as adenomyosis: hormone and other blood tests may be done to help to rule out other causes of symptoms such as heavy or painful periods, alongside imaging and examination
- Diabetes, thyroid disease, kidney disease and liver disease: these are monitored regularly with blood and urine tests
Why this matters in Singapore
Many of the conditions that clinical chemistry tests can detect are common in Singapore, and often have no symptoms in the early stages. The Ministry of Health’s National Population Health Survey for 2023 to 2024 found that about 1 in 11 residents aged 18 to 74 (9.1%) has diabetes, and about 3 in 10 (30.5%) have high blood cholesterol. About 1 in 3 has high blood pressure, which can damage the kidneys over time.
Diabetes is a leading cause of kidney failure in Singapore, which is why people with diabetes are advised to have their blood sugar, cholesterol and kidney function checked regularly. Hepatitis B, which can be detected through infectious serology, is a major risk factor for liver disease and liver cancer, and prostate cancer is the most common cancer in men here.
Regular check-ups matter. Singapore residents enrolled in Healthier SG may be eligible for subsidised or funded screening for conditions such as diabetes and high cholesterol, so ask your Healthier SG clinic for the current details.
Preparing for Your Test
Preparation depends on the tests that your doctor has ordered. Please follow the instructions that you are given. In general:
- Fasting: Some tests, such as blood glucose and lipids, may require you to fast for 8 to 12 hours so that the results are accurate. Plain water is usually allowed, unless you are told otherwise. Not all tests require fasting.
- Your medication: Ask your doctor whether to take your regular medicines before the test. Do not stop any medicine unless you are told to. Tell your doctor about all your medicines and supplements, including traditional or herbal medicines, and biotin (vitamin B7), which can interfere with some hormone tests and tumor markers.
- Drug level tests: For therapeutic drug monitoring, the timing of your blood test in relation to your last dose is important. Follow your doctor’s instructions about when to take your medicine on the day.
- Hormone tests: Some hormone tests need to be done at a specific time of the day, or on a specific day of your menstrual cycle. Your doctor will advise you.
- PSA test: Your doctor may advise you to avoid ejaculation, vigorous exercise such as cycling, or any recent prostate procedure for a short time before the test. Ask if this applies to you.
- Urine samples: You may be given a sterile container and shown how to collect a “midstream” sample, where you pass the first part of the urine into the toilet and then collect the middle part. Some tests need a 24-hour collection. Please follow the instructions carefully.
- Drinking water: Staying well hydrated makes blood collection easier, unless your doctor has told you to limit fluids.
- What to bring: Your doctor’s request form or referral letter, your NRIC (or passport if you are an international patient), and a list of your medications.
What Happens When Your Sample Is Taken?
- For a blood test, you will be seated comfortably, and an elastic band is placed around your upper arm. The skin is cleaned and a thin needle is used to collect blood from a vein. You may feel a brief pinch. The process takes only a few minutes.
- For a blood gas test, blood is usually taken from an artery, often at the wrist. This can be a little more uncomfortable than a normal blood test, and pressure is applied afterwards for a few minutes to stop any bleeding.
- For a urine test, you will be asked to pass urine into a sterile container.
- Your sample is labelled with your details and sent to the laboratory, where it is analysed by trained laboratory staff, using specialised equipment. The results are then checked and reported to your doctor.
What Happens After Your Test?
- You can return to your normal activities straight away, and eat and drink normally. If you were fasting, it is a good idea to have a meal and a drink soon after.
- Press on the blood collection site for a few minutes, and keep the plaster on for a few hours. A small bruise may appear and fades within days.
- Some results are ready within hours, while others, such as specialised hormone or drug level tests, may take a few days. Your doctor will tell you when to expect your results.
- You will be given a follow-up appointment to review your results with your doctor.
Understanding Your Results
- Each result is compared against a “reference range”, the range of values expected in healthy people. The range can differ between laboratories and between men, women and age groups, so always use the range shown on your report.
- A result outside the range does not always mean that you are ill. Eating before a fasting test, certain medicines, supplements, a recent illness, exercise or dehydration can all affect results.
- Your doctor will interpret your results together with your symptoms, medical history, examination and other tests. Your doctor may repeat a test, or order further tests, to confirm an abnormal result.
- Tumor marker results should never be read alone. A raised result does not always mean cancer, and a normal result does not always rule it out.
- Serology results show whether antibodies or other markers are present. These can mean a past infection, current infection or immunity, depending on the test, so your doctor will explain what yours mean.
- Results over time can be as useful as a single result. Keep your reports so that your doctor can compare them.
