General Health

When To Take A Blood Test After Fever?

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By Apollo 24|7, Published on- 17 August 2023

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Fevers are common occurrences, often signalling an underlying health issue. While most fevers resolve on their own, there are instances when a blood test for fever becomes necessary to determine the cause and guide appropriate treatment. A blood test reveals hidden insights about the body's response to the fever and its subsequent recuperation. In this blog post, information will be given on the timing of taking a blood test after a fever, and the importance of understanding blood test results accurately.

What is a Blood Test?

A blood test is a basic test that is done by taking a sample of blood from a person’s arm. It is usually done to gather information about a person's current health and enquire about other medical conditions. It helps detect and monitor various conditions, such as infections, inflammation, organ function, nutrient deficiencies, and more. Blood tests are conducted in laboratories using advanced equipment and techniques.

How Does a Blood Test Work?

A blood test includes the collection of blood samples from the arm of the affected person. This procedure is usually quick and relatively painless. The collected blood sample is sent to a laboratory for analysis after appropriately labelling it. 

In the laboratory, a series of fever panel tests are conducted with the blood sample to understand the different aspects of your health. Through the blood test, information about the components of the blood, like red blood cells, white blood cells etc can be gained. This test helps evaluate the overall health of your blood and can detect conditions such as 

  • Anaemia 
  • Infections
  • Blood disorders

Specific tests may be performed to assess the function of specific organs. For example, liver function tests examine markers and enzymes in the blood that can indicate liver health and detect liver diseases. These tests target specific markers, antibodies, or genetic material related to certain illnesses. 

Once the laboratory analysis is complete, healthcare professionals interpret the results based on established reference ranges and medical knowledge. The results help healthcare providers diagnose and monitor patients' health status, guiding appropriate treatment and interventions.

Signs and Symptoms of Fever

The following pointers will provide information on the common signs and symptoms of fever: 

  • Elevated body temperature: A rise in body temperature above the normal range of 100.4°F (38°C) aims at fever. The body raises its temperature as a response to an underlying health issue.
  • Sweating: Sweating is a common response to elevated body temperature and can lead to discomfort.
  • Chills: Chills manifest as sudden episodes of feeling cold or shivering, even if the surrounding environment is not cold. Chills occur as the body attempts to raise its temperature to match the elevated set point.
  • Headache: Headaches can also be caused by fever. Mild or severe headaches can be experienced by a person during fever.
  • Muscle aches: Fever can be accompanied by generalised muscle aches and body pain. The muscles may feel sore or tender, and movement can be uncomfortable or painful. Muscle aches are caused due to inflammation mostly. 
  • Fatigue: The body's energy resources are often diverted towards fighting off the underlying infection or condition, leading to feelings of exhaustion or lethargy.
  • Loss of appetite: During fever, individuals often find that they have a reduced desire to eat or a sense of taste. This can be due to the body's focus on combating the underlying illness.

When to Take a Blood Test After Fever?

The timing for taking a blood test after a fever depends on various factors that help determine the appropriate moment for accurate results. One crucial factor is the duration and severity of the fever. It is recommended to wait until the fever level decreases before taking a blood test. This is because an ongoing fever can affect certain blood parameters and potentially lead to misleading results.

Consult a doctor if you experience fever along with the following symptoms:

  • Headaches
  • Stiff neck
  • Difficulty breathing
  • Constant vomiting

Furthermore, the suspected cause of the fever plays a role in determining the timing of the blood test. If there is a specific suspected infection or condition, healthcare providers may recommend waiting until the fever has resolved to obtain more accurate results related to that specific issue.

Understanding Blood Test Results

Interpreting these results requires expertise, as they are reported as numerical values alongside reference ranges that indicate the normal levels for each parameter. 

1. Understanding Numerical Values and Reference Ranges

Blood test results are typically presented as numerical values that represent the concentration or activity of specific components in your blood sample. The components of blood include red blood cells, white blood cells, platelets, proteins, hormones, and many more. Each component has an associated reference range, which indicates the normal levels found in a healthy individual.

2. Interpreting Abnormal Results

Abnormal blood test results may indicate an underlying health condition. For example, an increase in levels of white blood cell counts could suggest an infection in the body, while abnormal liver function test results may point towards liver damage or disease. Similarly, a low level of vitamins or minerals in the blood can indicate nutrient deficiencies.


Blood tests are essential tools in diagnosing and monitoring health conditions, especially after experiencing a fever. The timing of a blood test after a fever is crucial to ensure accurate results. It is recommended to wait until the fever level decreases before undergoing a blood test. However, if the fever stays long or is accompanied by severe symptoms, immediate medical attention is necessary. Consultation with a healthcare professional who can interpret the blood test results accurately and guide you towards appropriate treatment and care is necessary. 

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1. Can I take a blood test during the fever?

It is recommended to wait until the fever level decreases and then take a blood test to ensure accurate results.

2. How long should one wait to take a blood test after a fever?

It is better to wait until the fever subsides before taking a blood test. This helps in getting an accurate interpretation of the results.

3. Can a blood test determine the cause of a fever?

Yes, a blood test can determine the cause of the fever. It can provide valuable information about the various causes of a fever, such as an infection, or any other medical conditions.


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