Hypovolemia: symptoms, causes, diagnosis and treatment.


When the amount of fluid in the intravascular system is too small, it is called insufficient volume or hypovolemia. (In most cases, this refers to blood volume, but it can also include lymphatic fluid.) This article will focus on hypovolemia, as it refers to the volume of blood in relation to the available space within the circulatory system .

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The need for fluids for each person is slightly different and depends on muscle mass, the state of the cardiovascular system, body fat and many other factors. There are clinical signs of hypovolaemia, but it is possible to lose up to 30% of total circulation before signs or symptoms of hypovolaemia become apparent .


The body is a bag (or bags) of fluid. Each cell has a fluid-filled outer membrane, within which are all the structures necessary for the cell to function. Cells form tissues , many of which are organized into various structures that leak or contain fluid.

All of this liquid is water-based and must contain enough water to balance all the salts and particles it contains. Water and salt travel from cell to cell and in and out of the bloodstream as the body needs to balance fluids.

When the body is sufficiently hydrated and there is a relative volume of fluid sufficient to fill the available blood space, the systems generally function properly.

However, when the blood space is too large compared to the available fluid, it is called hypovolemia.

Lack of volume affects the body's ability to adequately perfuse (fill) tissues with blood, oxygen, and nutrients. Insufficient perfusion is a condition known as shock . Hypovolemia and shock are closely related .


The symptoms of hypovolemia and shock are very similar. As blood volume decreases, the body begins to compensate for the lack of volume by narrowing the blood vessels. Compression of the blood vessels reduces the available space within the cardiovascular system, which means that the relative volume of blood is sufficient to generate pressure and perfuse the tissues .

This drains blood from the most distal parts of the body (usually the skin) and results in less noticeable discoloration and heat (cold, pale skin). The heart rate increases to allow faster circulation of available blood and to raise blood pressure enough to compensate for the loss of volume (and pressure) in the vascular space. At this stage, the measured blood pressure often changes very little.

If the cause of hypovolemia (see below) persists and the body continues to lose fluid, the body reacts as follows :

  • Sweating (stress response to loss of perfusion)
  • Dizziness (as loss of perfusion affects the brain)
  • Confusion
  • Fatigue
  • Low blood pressure

If hypovolemia is not treated and the cause is not eliminated, the patient may lose consciousness.


Generally, 60% of body weight in men is liquid, while in women it is about 50% .

There are several ways to lose fluid volume. Sweating, profuse urination, vomiting, or diarrhea can cause rapid loss of water. If the fluid is not replenished with drinking water, a person can become dehydrated and eventually hypovolemic.

Bleeding is the most common cause of hypovolemia. In fact, direct blood loss can lead to hypovolemia very quickly.

The site of bleeding can be internal (for example, bleeding in the abdominal cavity), gastrointestinal (bleeding in the stomach, esophagus, or intestines), or external. In cases of internal or gastrointestinal bleeding, sometimes the signs and symptoms of hypovolemia are the first signs of bleeding rather than the observation of the bleeding itself.

Removal of fluid from the bloodstream can also cause hypovolemia. Severe dehydration (water loss) can lead to hypovolemia as the tissues draw water from the bloodstream to balance the loss. Even a patient with severe swelling (swelling) of the extremities, for example, a patient with congestive heart failure, may have hypovolemia .

Even if the patient may have too much fluid in the body (resulting in edema), there may not be enough fluid for the cardiovascular system. This will lead to hypovolemia.

If the amount of fluid in the body has not changed, but the size of the cardiovascular system has increased, the patient may experience relative hypovolemia. In this case, there is no fluid loss or movement, but the sudden increase in space in the blood vessels results in the same loss of pressure and perfusion as hypovolemia. This is the reason why the patient loses consciousness during fainting .


There is no definitive blood test for hypovolemia. A clinical evaluation is required to make a diagnosis. Vital signs, including blood pressure, pulse rate, capillary filling time (how long it takes for color to return to nails after squeezing; the faster it comes back, the better), and respiratory rate all provide tracks. The patient's blood volume. regarding your cardiovascular system .

By taking a complete history and physical exam, the doctor may ask the patient about fluid intake, history of vomiting or diarrhea, and urine output. The patient may also need to measure blood pressure and heart rate while lying down, sitting, and standing. Changes in vital signs between these positions may indicate the presence of hypovolemia.

Watch out

Fluid intake is a treatment for hypovolemia . In the case of direct blood loss in severe cases, a blood transfusion may be necessary. Otherwise, IV fluids may be required. The most important treatment is to address the underlying cause of the hypovolemia .

Get the word of drug information

Hypovolemia can cause shock, and shock is very dangerous. If you haven't been getting enough fluids or have had bleeding (even simple nosebleeds that won't stop) and you feel dizzy, weak, or nauseous, it's best to see your doctor or healthcare professional right away. Early intervention is the best for diagnosis and treatment.

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