28 November 2023

Why do You Have to Fast Before Having a Health Check?

The nutritional content in the food and drinks you consume before taking a health test will be absorbed into the bloodstream.

Why do you have to fast first before having a health check?

To ensure that your test results are accurate. Because the nutritional content in the food and drinks you consume before taking a health test will be absorbed into the bloodstream and can have a direct impact on blood glucose, fat and iron levels in the body.

Several types of examinations require the patient to fast before the examination, namely:

• Glucose check
• Cholesterol examination (lipid/fat profile)
• Check triglyceride level
• Basic metabolic system examination

How long to fast before the examination?

The fasting time is around 10-12 hours before carrying out the examination. It is permissible to drink water so that the body remains well hydrated so that it will give an idea of the actual examination levels. It is best to take blood in the morning, when the body is still fit after resting at night.

What are the consequences if you don't fast before the medical check-up?

If you do not fast or fast for not the recommended time, the examination you carry out will give inaccurate results because certain examinations are influenced by food.

Can I take medicine before having a health check?

There are several drugs that will impact blood test results. However, if you are required to continue taking medication, inform the laboratory, with the aim of assisting the laboratory in validating your health test results.

Why can't you drink coffee, smoke and drink alcohol before a health check?

• Effects of caffeine

Caffeine is found in various types of food that are ingested every day. May increase blood glucose concentration.

• Effects of smoking

Smoking increases plasma/serum concentrations of fatty acids, epinephrine, free glycerol, aldosterone and cortisol.

These changes occur within an hour after smoking 1-5 cigarettes. Changes in analytes caused by chronic smoking include blood leukocyte counts, lipoproteins, activity of several enzymes, vitamins hormones, tumor markers and heavy metals.

The degree of change also depends on the amount, type (cigerattes, cigars, pipes) and smoking technique (with or without inhalation). In addition, changes caused by smoking are influenced by age and gender.

The image below shows the concentrations of cotinine, thiocyanate and carboxyhaemoglobin, used as markers for qualitative and quantitative assessment of smoking habits. Cotinine has the advantage of having a longer half-life (20-28 hours) than nicotine, the parent compound (12-15 minutes).

• Effects of alcohol

Alcohol consumption, depending on duration and extent, Acute effects (within 2-4 hours) of ethanol consumption are a decrease in serum glucose and an increase in plasma lactate. Increased lactate reduces urinary uric acid excretion. Consequently, after acute alcohol consumption, serum uric acid concentrations increase.

Chronic effects of ethanol consumption include increased serum activity of the liver enzyme, g-glutamyltransferase (GammaGT) caused by enzyme induction. Glutamate dehydrogenase as well as aminotransferase (AST, ALT) activity is increased due to direct liver toxic effects. In chronic alcoholism, serum triglycerides increase due to decreased breakdown of plasma triglycerides. The increase in MCV may be related to direct toxic effects on erythropoietic cells or folate deficiency.

Reviewed by : dr. Widi Angga Kusuma, M.K.K.

Source :

• Sample From the patient to the Laboratory page 15 edition 2, 2001, W.G. Guder, S. Nayaranan, H. Wisser, B. Zawta https://hellosehat.com/sehat/information-kesehatan/kenapa-perlu-cepat-puasa-prior-periksa-kesehatan

Picture : freepik.com