How to prepare for a blood test

Proper preparation for the test is essential for obtaining reliable results.

Most tests should be carried out while fasting – i.e. without breakfast, between 7 and 9 am. For tests that include lipid and liver profiles, it is also recommended that you have a light evening meal by 6 pm on the day before the test.

You should not undergo testing after a sleepless night or strenuous physical activity. Any medication to be taken on the day of the test must be agreed with your doctor and be directly related to the purpose of the test. Samples for measuring medication levels are collected before the morning dose or at peak absorption. For some tests, such as aldosterone, body position and the time of day are also important.

Blood samples must be collected while fasting because levels change after a meal:

– glucose
– glucose tolerance test
– insulin
– C-peptide
– lipid parameters (TG, HDL)
– iron
– phosphorus
– cortisol
– folic acid

Blood samples should be collected in the morning because of the circadian rhythm:

– iron
– phosphorus
– potassium
– zinc
– copper
– cortisol
– aldosterone
– ACTH
– prolactin
– FSH
– LH
– oestriol
– TSH
– growth hormone
– PTH
– testosterone
– 17-OH-progesterone
– DHEA
– erythropoietin

Blood collection in the morning while fasting is recommended:

– coagulation parameters (PT, APTT, fibrinogen)
– magnesium
– calcium
– urea
– creatinine
– uric acid
– prolactin
– total protein
– bilirubin
– AST
– ALT
– ALP
– LDH
– full blood count
– ESR