Fluish Feeling Meaning and Causes of Flu-Like Sensation

What is the fluish feeling?

At times a person may feel unwell or is in discomfort without being able to identify any specific symptoms like nausea or pain. It is a generalized sensation that cannot be localized to a certain part of the body. This is commonly referred to as a fluish feeling or a flu-like feeling. The correct medical term for this sensation is malaise. The flu (seasonal influenza) is the most common recurrent ailment that humans experience throughout life. One of the main features of this viral infection is malaise which precedes the other symptoms and persists throughout the illness. Therefore it is only natural that most people describe malaise as feeling fluish or a flu-like sensation since they are very familiar with this sensation.

Meaning of Fluish Feeling

There is no specific explanation for malaise or the fluish feeling. It is a sensation that cannot be definitely measured and may vary from person to person. Although subjective, some features that may be noted includes :

  • Fatigue (tiredness)
  • Dizziness or lightheaded
  • Changes in blood pressure
  • Changes in heart rate
  • Changes in blood glucose
  • Changes in blood gas levels
  • Nausea
  • Irritability

The severity of these symptoms may vary from person to person and is also dependent on the underlying cause. However, it is important to note that a fluish feeling is not always due to the flu (influenza) or any related systemic infection. It may be experienced with a number of conditions like diabetes mellitus, heart attack, cancer or autoimmune diseases. Even in these instances, malaise may precede the onset of other more definitive symptoms.

Therefore a fluish feeling should not be taken as a sign of the upcoming flu particularly in a person who is at high risk of developing other conditions. This especially applies to people over the age of 40 years, who are obese, with a history of cigarette smoking and family history of ailments like heart attacks, stroke, diabetes and cancer. The elderly need to be particularly cautious with regards to a fluish feeling.

Causes of Fluish Feeling

Malaise is a common symptom in a wide range of conditions. It may occur for a short period in acute diseases or acute flareups of chronic diseases. Sometimes malaise is persistent for much longer periods – even months and years.


Infections are one of the most common cause of the fluish feeling even when it is not the influenza virus involved. It is the systemic infections, most of which are viral, that are more likely to contribute to malaise.

  • Influenza – seasonal flu and H1N1 (swine flu)
  • Lyme disease
  • Rhinovirus infection (common cold)
  • Malaria
  • Chronic viral hepatitis
  • Tuberculosis

There are various other systemic infections that cause cause malaise. The presence of a fever and swollen lymph nodes is a common indicator of an infection. Travelers to endemic areas, particularly in developing nations without proper vaccinations, should be cautious about malaise as it may be the first sign of an infection.

Heart and Blood Vessels

Any condition that compromises heart function will lead to malaise. This includes changes to heart rate and rhythm. Blood can therefore not be adequately re-oxygenated and distributed throughout the body as is usually the case. Vascular conditions are less likely to cause malaise.

  • Myocardial infarction (heart attack)
  • Congestive cardiac failure (CCF)
  • Pericarditis, especially viral pericarditis
  • Stroke
  • Vasculitis

Lungs and Airways

Reduced lung function or constriction of the airways hampers gas exchange with the blood and therefore its oxygenation or the flow of oxygen rich air into the lungs. The subsequent build up of carbon dioxide in the blood (hypercapnia) and changes in blood pH may also be contributing factors to malaise associated with the respiratory system.

  • Chronic obstructive pulmonary disease (COPD)
  • Acute bronchitis
  • Pulmonary tuberculosis (lung TB)
  • Bronchiectasis

Glands and Hormones

Endocrine disorders are diseases pertaining to the glands and hormones. These structures and chemicals are responsible for regulating almost all activity in the body, including the metabolic rate, water and electrolyte levels, and blood glucose. Although symptoms of endocrine dysfunction is not always apparent immediately, dysfunction tends to lead to non-specific symptoms such as malaise.

  • Diabetes mellitus (sugar diabetes)
  • Underactive or overactive thyroid gland
  • Adrenal gland disorders
  • Pituitary gland dysfunction

Immune System

Autoimmune disorders where the immune system turns against the body’s own tissues may present with malaise apart from localized symptoms pertaining to the organ that is affected. Immune deficient states where the immune defenses are weakened may increase the chances of recurrent infections from various pathogens. Malaise may sometimes be a constant feeling apart from the symptoms specific to each infection.

  • Systemic lupus erythematosus (SLE)
  • Rheumatoid arthritis
  • Long term diabetes mellitus

A flu-like feeling can occur shortly after vaccinations but is usually short-lived. This is a response of the immune system as it develops protection against the specific disease.


Malignant tumors may also contribute to malaise even when the cancer is well localized. However, it is cancers such as leukemia and lymphoma that are more likely to present with non-specific symptoms like malaise for a long period of time even in the absence of other symptoms. Some cancers produce and secrete certain hormone-like substances into the bloodstream – carcinoid syndrome. Metastatic spread involving cancer on multiple sites, chemotherapy and radiation therapy are among the more common cancer causes of malaise.


The most common hematological causes of malaise is severe anemia. However, changes in blood pH and a build up of wastes in the bloodstream (uremia) associated with kidney disorders are other common causes. Very serious cases includes septicemia where there is an accumulation of bacterial toxins in the bloodstream.


The psychiatric causes of malaise is largely associated with depression. There may be no change in any of the usual systems that are affected in malaise. Rather the low quantities of serotonin and the subsequent depressed mood may be mistaken for a fluish feeling. Sometimes it is entirely psychogenic meaning that it is imagined rather than being associated with actual changes in the body. Many psychiatric drugs cause malaise.

Medication and Substances

Prescription medication that may contribute to malaise includes :

  • Antihistamines
  • Antiretrovirals for HIV/AIDS
  • High blood pressure medication
  • Seizure drugs

Drug interactions where there is a reaction with the use of two or more medication simultaneously may also be responsible for malaise. Alcoholism, accidental or intentional poisoning and the use of illicit drugs can all contribute to malaise even after these substances wear off and have been removed from the system.

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