What Is Hypovolemia?

A Severe Lack of Circulating Fluids

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Hypovolemia is the loss of 15% or more of the fluid circulating in the body, specifically blood or water. Because your organs need these fluids to function, their depletion can cause organs to malfunction and fail. Symptoms include dizziness, rapid heartbeat, clammy skin, confusion, and fainting.

There are many possible causes for hypovolemia from extreme dehydration or massive bleeding. In severe cases, hypovolemia can lead to shock and death.

This article describes the symptoms and causes of hypovolemia. It also explains how this potentially serious condition is diagnosed and treated.


Hypovolemia should not be confused with dehydration. Hypovolemia is the decreased volume of fluid in the vascular system (blood vessels and lymphatic vessels) with or without whole-body fluid depletion. Dehydration is the depletion of whole-body fluid.

Hypovolemia can occur as a result of dehydration but can also occur independently of it.

Woman pouring water into a glass
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How Hypovolemia Occurs

Hypovolemia literally means low (hypo-) volume (-volemia). It involves a decrease in the volume of extracellular fluids. Extracellular fluids are those that exist outside of cells, such as the fluid part of blood (known as plasma) or the fluid circulating in lymphatic vessels (known as lymph).

Hypovolemia is ultimately caused by either a loss of blood or a loss of water. In either instance, the depletion of fluid decreases the volume of whole blood in the body. This, in turn, reduces the amount of oxygen being delivered to cells and tissues throughout the body.

When hypovolemia becomes severe, the low volume of blood in arteries and veins will cause your blood pressure to drop. When it drops to where organs are unable to function, the body goes into shock.

Shock caused by hypovolemia is specifically known as hypovolemic shock.

What Are the Symptoms of Hypovolemia? 

Hypovolemia causes systemic symptoms, meaning that the whole body is affected by the reduced flow of blood. The symptoms worsen as fluid volumes in the body continue to drop.

Hypovolemia symptoms may not be recognized in the early stages and may only become apparent when the volume depletion approaches 30%.

Hypovolemia is categorized into stages 1 through 4, which denote the percentage of fluid volumes lost. Symptoms develop in a characteristic pattern from stage to stage, as follows:

 Stage 1 Up to 15% loss Stage 2 15-30% loss Stage 3 30-40% loss  Stage 4 Over 40% loss 
Pale skin Pale, clammy skin Excessive sweating Excessive sweating with mottled or bluish skin
Cooler skin temperature Slightly elevated heart rate Heart rate over 120 beats per minute (bpm) Heart rate over 140 bpm with a weak pulse
Dry mouth Slightly elevated breathing rate Rapid, shallow breathing Extremely rapid, shallow breathing
Increased thirst Fatigue Exhaustion with normal activity Extreme lethargy
  Anxiety and restlessness Dizziness and lightheadedness Altered consciousness
  Decreased urination Confusion and an altered mental state Little to no urine output
    Significantly decreased urine output Fainting

Hypovolemic Shock

In medical terms, shock is the body's response to a sudden drop in blood pressure.

Hypovolemic shock is a type of shock in which severe blood or fluid loss makes the heart unable to pump enough blood to service the body's needs. Other types include cardiogenic shock (related to the dysfunction of the heart) and anaphylactic shock (caused by a severe allergic reaction).

Hypovolemic shock is a medical emergency that develops in a progressive pattern. It technically starts with stage 1 hypovolemia and progresses to stage 4, at which point the insufficient flow of blood can start to damage the heart, lungs, liver, kidneys, and other vital organs.

If left untreated, multiple organ failure can occur. If treatment is not delivered quickly, the risk of irreversible damage and death is high.

Risk of Death

According to a 2022 study in JAMA Network Open, roughly one in three people who experience shock outside of a hospital die within 30 days, even with medical treatment.

What Causes Hypovolemia? 

Hypovolemia can range from mild to severe depending on the underlying cause. Common causes include:

How Is Hypovolemia Diagnosed? 

There is no definitive blood test for hypovolemia. A clinical assessment is required to diagnose it. Vital signs are evaluated, including:

  • Blood pressure
  • Heart rate
  • Respiratory rate
  • Capillary refill time (the amount of time it takes for the color to return to your fingernails after you squeeze them—the faster it returns, the better)

These all give clues about someone's blood volume relative to their cardiovascular capacity.

When doing a thorough history and physical exam, your healthcare provider may ask about fluid intake, history of vomiting or diarrhea, and urine output.

You may also need to have your blood pressure and pulse taken while lying down, sitting up, and standing. Changes in the vital signs between these positions could indicate the presence of hypovolemia.

How Is Hypovolemia Treated? 

Fluid intake is the treatment for hypovolemia. The type of fluids used for hypovolemia will depend on the individual case and the cause of the condition, and why an intravenous infusion may be required.

In the case of direct blood loss, a blood transfusion could be necessary for severe cases. The most important treatment is to correct the underlying cause of the hypovolemia.


Hypovolemia is the loss of 15% or more of circulating fluids in the body. Causes include severe dehydration, internal or external blood loss, and severe illnesses that cause fluids to accumulate in the body cavities. Symptoms can progress from fatigue, clammy skin, and dizziness to rapid heartbeats, changes in consciousness, and fainting.

Depending on the cause, hypovolemia may be treated with intravenous or oral fluids or with a blood transfusion. Severe cases can lead to a medical emergency known as hypovolemic shock.

5 Sources
Verywell Health uses only high-quality sources, including peer-reviewed studies, to support the facts within our articles. Read our editorial process to learn more about how we fact-check and keep our content accurate, reliable, and trustworthy.
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By Rod Brouhard, EMT-P
Rod Brouhard is an emergency medical technician paramedic (EMT-P), journalist, educator, and advocate for emergency medical service providers and patients.