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5 Precautions You Must Take Before a Lab Test


If you have ever suffered from any health irregularities or had symptoms of a disease, the doctor had suggested you go through a few lab tests for diagnosis.

The doctors perform these tests to find the possibility of any disease and analyze your health conditions. They also ask you to take some precautions before lab tests. Let’s discuss this in this article.

What’s in it-

What is a Lab Test?

Laboratory tests are medical devices that are intended for use on samples of blood, urine, or other tissues or substances taken from the body to help diagnose disease or other conditions. In the lab test, the doctor takes your blood sample, urine sample or body tissues to determine the possibility of a disease according to the symptoms.

Common Lab Tests

The blood is responsible for the flow of all the nutrients, fluids, and oxygen in different parts of the body. A blood test indicates all the unwanted changes in the body through different medical investigations. Few tests are the primary considerations of doctors in maximum cases. Generally, these tests are enough to diagnose the cause of irregularities in the body.

Complete Blood Cells- CBC is the most common test performed to check the different components in the blood, such as red blood cells, white blood cells, platelets, haemoglobin, hematocrit, etc.

Prothrombin Time- This test tells how much timetheblood takes to clot by measuring the essential factors of blood clotting.

Lipid Profile- Lipid profile test checks the risk of heart disease by measuring the level of two types of cholesterol-

High-density lipoprotein (HDL) or good cholesterol.

Low-density lipoprotein (LDL) or bad cholesterol.

Liver Panel- This test determines the liver functioning and identifies the possibility of liver disorders.

Thyroid Profile- Thyroid profile test measures thyroid-stimulating hormone levels in the blood which are related to the thyroid gland.

Basic Metabolic Panel- The BMP test checks the level of certain compounds in the blood, such as calcium, glucose, electrolytes, sodium, potassium, chloride, carbon dioxide, blood urea nitrogen, and creatine.

Comprehensive Metabolic Panel- The comprehensive metabolic test is a complete test that includes all the measurements of BMP. It contains around six additional tests to check the compounds related to liver function.

Hemoglobin A1c Test- Hemoglobin is a protein found in red blood cells. HbA1c test helps to determine the risk of diabetes by measuring the blood sugar level, either high or low.

Urinalysis- This is a screening test used to detect the early signs of any disease by collecting urine samples.

Precautions Before Lab Test

Many routine habits or biological factors can affect the results of a lab test due to incorrect readings. Hence, whenever you go to a doctor or the pathologist for the diagnosis of any disorder in your body, they suggest you take a few precautions before performing the lab test.

Let’s discuss in detail all those precautions that you should take before the lab test.


Fasting is the most common precaution that every doctor advises in almost every blood test. Before 8 hours of giving a blood sample, the patient is not allowed to eat anything and only drink water. It is necessary because our body absorbs the nutrients present in the food and it may bring some chemical changes in our body. Fasting helps to get accuracy in the results of the tests. Every blood test doesn’t require fasting. But, following blood tests can get affected by the previous meals-

  • Blood sugar test
  • Liver function test
  • Cholesterol test
  • Renal panel test
  • Triglyceride level test
  • Basic metabolic panel

Generally, the duration of fasting before the lab test is 8 hours. But in some cases, a patient needs to fast for at least 12 hours before the test.

Hence, the doctors perform most of the tests in the morning because bedtime is also a fasting time, and it is the best time to expect a higher accuracy of test results.

Diet and Nutrition

If your doctor didn’t ask you about your daily lifestyle, then you should tell him about your daily routine and diet practice from your side. If you are not habitual of drinking enough amount of water, it may cause dehydration, and it might also be responsible for the unexpected results of the test.

Hence, it’s good to tell your doctor about your diet before the test.


It may happen that you are going for a lab test for the diagnosis of a disease, but already taking medicines due to any previous health issues. If you are following a medicine routine, you might have to discontinue it before 2-3 days of tests to avoid the alteration in your reports. The reason behind this is that medicines contain various types of drug components.

Even if there is no need to stop the consumption of any medicine, you must share the prescription with your doctor so that they can consider this factor to interpret the results of your tests.


During pregnancy, many women experience psychological changes. Also, variation in renal and liver functions, hormone levels is common. These changes can reflect in the medical reports as well. So, inform your doctor about such conditions.

It is necessary because, during different stages of pregnancy, doctors consider different reference ranges to measure the values of various components in the blood. These reference ranges differ from general range.

Previous Disorders

If you had any past medical complication, Few of the micro-organisms associated with that disease might be still there in your blood even after cure. Moreover, a heredity health issue can also affect the readings of the test results. It is good to inform your doctor in advance about the health history of your family so that he will keep those points in mind.

There are a few more things that you must take care of before drawing your blood samples. Following are the factors that can also affect your lab test results-

  • You can drink water in the duration of fasting, but you must avoid drinking carbonated beverages or any juices.
  • Tea and Coffee contain caffeine. It increases the amount of pee and causes your body to expel more water. It ultimately dehydrates your body and may affect the test result.
  • Consumption of alcohol leaves its traces for a few days in your blood. Hence, you avoid it, especially before the triglyceride level test.
  • Smoking cigarette before an hour of test schedule reduces the activity of enzymes due to the presence of nicotine. So, take care of this point before lab test if you are a smoker.


So, you have got to know useful information about the various lab tests, and various precautions that you must take before going for a lab test. After collecting your blood sample, doctors perform a group of tests to analyze the working of different body functions. Eat some snacks or take some juice after drawing your blood to provide the energy to your body. Do not remove the bandage immediately. Keep it at the point of the needle for some time so that it does not keep bleeding. The pathologist divides blood sample into many parts and performs different tests on each sample. It takes a few hours to analyze those samples, and you can get the report within 24 hours.

Also you can read our blog on Fatty Liver Disease | Stay Cautious before it turns fata


Can I drink milk before the lab test? It is okay if you drink plenty of water before a lab test. But, don’t take any other drink than water or else you have to face problems in the accuracy of results. Q. What will happen if I don’t fast before the test? If you do not fast before the test, then the doctor will get the deviated readings according to the food you have eaten, and ultimately the report of your sample will show inaccurate results. Q. What is the reference range in a blood test? The reference range is a standard numeric range of results. It is derived by testing healthy human bodies, and an average assumption is the reference range for the readings of all the tests. Q. Does exercise affect the lab test results?

Yes, regular exercise increases the activity level of the body. Heavy workouts can also change the thyroid functions. These may affect some lab parameters.