They may feel that something is wrong even before they can clearly describe their symptoms.

Cold sweating can also occur when the body is under significant physical stress.

Why might this happen?

When the body experiences respiratory distress, the nervous system activates stress responses.

The heart may beat faster, breathing may become more rapid, and sweating may increase.

These reactions are part of the body's response to physical stress.

However, sweating and anxiety are highly nonspecific symptoms.

They can also occur with:

• Panic attacks.

• Low blood sugar.

• Fever.

• Pain.

• Heart rhythm abnormalities.

• Heart attacks.

• Dehydration.

• Medication reactions.

How can you distinguish anxiety from a medical emergency?

It is not always possible to distinguish them without medical assessment.

Panic attacks can cause intense breathlessness, chest tightness, dizziness, and a racing heart.

But serious respiratory and cardiovascular conditions can produce similar symptoms.

A person should not assume that new or severe breathing difficulty is simply anxiety.

If cold sweating occurs with chest pressure, faintness, severe breathlessness, or confusion, seek emergency help.

What Causes Blood Oxygen Levels to Fall?

The eight symptoms above may occur when oxygen delivery is impaired, but they do not all have the same underlying cause.

Understanding the possible causes helps explain why some people experience sudden oxygen problems while others develop gradual changes over months or years.

1. Lung Diseases

The lungs are responsible for transferring oxygen from inhaled air into the bloodstream.

Any condition that interferes with this process can potentially lower blood oxygen.

Pneumonia

Pneumonia is an infection that causes inflammation in the lungs.

The tiny air sacs responsible for gas exchange may become filled with fluid and inflammatory material.

This can make it harder for oxygen to enter the bloodstream.

Symptoms may include:

• Fever.

• Cough.

• Chest discomfort.

• Breathlessness.

• Fatigue.

• Rapid breathing.

Severe pneumonia can cause significant oxygen deficiency and may require hospital treatment.

Older adults and people with chronic medical conditions may develop serious illness even when their initial symptoms seem relatively mild.

Chronic Obstructive Pulmonary Disease

COPD is a group of progressive lung conditions that includes emphysema and chronic bronchitis.

The disease can narrow airways, increase mucus production, and damage lung tissue.

As the condition progresses, some people develop difficulty maintaining adequate oxygen levels.

Warning symptoms include persistent cough, wheezing, breathlessness, and reduced exercise tolerance.

Smoking is a major risk factor, although other exposures and genetic factors may contribute.

Asthma

Asthma causes inflammation and narrowing of the airways.

During an asthma attack, the airways become more restricted, making it difficult to move air in and out of the lungs.

People may experience wheezing, coughing, chest tightness, and shortness of breath.

Severe attacks can become life-threatening.

A person with asthma should follow their prescribed action plan and seek emergency help if symptoms are severe or do not respond to their rescue treatment as instructed.

Pulmonary Fibrosis

Pulmonary fibrosis involves scarring of lung tissue.

The scarring makes the lungs stiffer and can interfere with oxygen transfer.

Symptoms may include progressive breathlessness, dry cough, fatigue, and reduced ability to exercise.

The condition can have several causes, including autoimmune disease, certain medications, occupational exposures, or no identifiable cause.

2. Heart Conditions

The heart and lungs work together to deliver oxygen throughout the body.

Even when the lungs take in sufficient oxygen, problems with the heart can interfere with circulation and oxygen delivery.

Heart Failure

Heart failure occurs when the heart cannot pump blood effectively enough to meet the body's needs.

Fluid may accumulate in the lungs, making breathing more difficult and interfering with gas exchange.

Possible symptoms include:

• Breathlessness during activity.

• Difficulty breathing while lying flat.

• Waking up suddenly at night feeling breathless.

• Swelling in the legs or ankles.

• Unusual fatigue.

• Rapid weight gain due to fluid retention.

Some people with heart failure may develop low oxygen levels, particularly during episodes of worsening disease.

Abnormal Heart Rhythms

Certain arrhythmias can cause the heart to beat too quickly, too slowly, or irregularly.

When circulation becomes inefficient, the body may not receive enough blood flow.

Symptoms can include palpitations, dizziness, weakness, breathlessness, or fainting.

Not every arrhythmia causes low oxygen saturation, but persistent or severe symptoms require assessment.

3. Severe Infections and Sepsis

Sepsis is a life-threatening response to infection that can cause organ dysfunction.

It may develop from infections involving the lungs, urinary tract, abdomen, skin, or other parts of the body.

Sepsis can affect circulation, blood pressure, and organ function.

In severe cases, it may lead to respiratory failure and inadequate oxygen delivery to tissues.

Warning signs can include:

• Confusion.

• Rapid breathing.

• Rapid heart rate.

• Fever or unusually low body temperature.

• Severe weakness.

• Cold or clammy skin.

• Reduced urine output.

Sepsis is a medical emergency. Do not wait for every symptom to appear before seeking help.

4. Pulmonary Embolism

A pulmonary embolism occurs when a blood clot blocks an artery in the lungs.

Many clots originate in deep veins, often in the legs, before travelling through the bloodstream to the lungs.

A large or strategically located clot can interfere with blood flow through the lungs and place serious strain on the right side of the heart.

Possible symptoms include:

• Sudden shortness of breath.

• Chest pain, sometimes worse with deep breathing.

• Rapid heartbeat.

• Coughing, occasionally with blood.

• Dizziness or fainting.

Some people may also have swelling, pain, warmth, or redness in one leg due to deep vein thrombosis.

A suspected pulmonary embolism requires emergency medical evaluation.

5. Anemia and Reduced Oxygen-Carrying Capacity

Anemia occurs when the blood has insufficient healthy red blood cells or hemoglobin to carry oxygen effectively.

It is important to understand that anemia and hypoxemia are not the same condition.

A person with anemia may have a normal oxygen saturation reading because the hemoglobin that remains can still be well saturated.

However, the total amount of oxygen carried in the blood may be reduced.

Common symptoms include:

• Fatigue.

• Weakness.

• Pale skin.

• Dizziness.

• Breathlessness during activity.

• Rapid heartbeat.

Iron deficiency is one common cause of anemia, but vitamin B12 deficiency, folate deficiency, chronic disease, blood loss, and inherited conditions can also contribute.

Treatment depends on the underlying cause. Taking iron supplements without confirming iron deficiency is not always appropriate.

6. Sleep Apnea

Sleep apnea is a sleep-related breathing disorder in which breathing repeatedly becomes interrupted or reduced during sleep.

Obstructive sleep apnea occurs when the upper airway becomes partially or completely blocked.

These interruptions can cause repeated drops in oxygen saturation during the night, along with disrupted sleep.

Possible symptoms include:

• Loud snoring.

• Pauses in breathing noticed by another person.

• Gasping or choking during sleep.

• Morning headaches.

• Daytime sleepiness.

• Difficulty concentrating.

• High blood pressure.

Not everyone with sleep apnea is overweight, and not everyone who snores has the condition.

If you regularly wake up exhausted despite spending enough time in bed, or someone notices repeated breathing pauses, consider discussing a sleep assessment with a healthcare professional.

How to Measure Blood Oxygen Levels at Home

A pulse oximeter is a small device that usually clips onto a fingertip.

It uses light to estimate the percentage of hemoglobin carrying oxygen in the blood.

This measurement is called oxygen saturation, commonly abbreviated as SpO₂.

The device may also display pulse rate.

Pulse oximeters are widely used in hospitals and can also be useful for certain people monitoring their health at home.

However, the reading is an estimate, not a direct measurement of oxygen in the blood.

What Is a Normal SpO₂ Reading?

For many healthy people at sea level, oxygen saturation is commonly around 95%–100%.

However, the appropriate range may differ depending on medical history, chronic lung disease, altitude, and individual circumstances.

Some people with chronic respiratory conditions may have a lower prescribed target range.