What Makes Oxygen Saturation (SpO2) Levels Fluctuate?

Since COVID-19 made us all more cognizant of our oxygen saturation levels (SpO2 levels), questions arose about what affects it. The term SpO2 levels refer to saturation of peripheral oxygen. Measured using a pulse oximetry, it expresses the fraction of oxygen-saturated hemoglobin relative to unsaturated and saturated hemoglobin in the blood.

Do SpO2 Levels Fluctuate?

The normal pulmonary function requires a healthy SpO2 level. A healthy human adult should typically have 95% to 99% oxygen saturation, the normal oxygen levels. A resting SpO2 of less than 89% raises concern. Many everyday events temporarily cause SpO2 to fluctuate without cause for concern. These activities or reasons include exercise and the fight or flight syndrome that our body activates when under extreme duress.

Do SpO2 Levels Drop during Exercise?

When exercising, a normal, healthy person experiences a drop in SpO2 levels to about 92%. The energy expended by the body’s muscles during a workout lowers the blood oxygen level temporarily. Do your best to regulate your breathing during workouts. Training yourself to breathe deeply and draw in oxygen from around you can help you maintain a proper amount of O2 in your blood.

When you breathe hard during a workout, your body recognizes its need to take more oxygen and expel carbon dioxide. Your heart works harder to supply more oxygen to your muscles and rid itself of some carbon dioxide.

The human body adjusts to workouts to handle the exertion better. This results in less heavy breathing because SpO2 levels didn’t drop as much. A measurement of 88% to 92% during fitness training isn’t a cause for concern, provided that it’s temporary.

Are SpO2 Levels Lower When Sleeping?

Yes, blood oxygen levels normally drop slightly during sleep to about 95%, according to the American Sleep Apnea Association (AASM). The drop depends on your body’s typical resting measurement. A normal waking blood oxygen level of 94% usually results in a sleep oxygen level of about 88%.
If your blood oxygen levels regularly drop below 90%, it could indicate hypoxemia or other health issues, ranging from sleep apnea to chronic obstructive pulmonary disease (COPD). Asthma and emphysema can also cause these abnormally low levels, as can some heart diseases.

Can Common Cold Reduce SpO2?

Yes, something as simple as the common cold can affect the normal SpO2 values. It causes a variation of 3% to 4%. If your resting SpO2 falls below 90%, see a doctor immediately. That indicates potential acute respiratory failure. You might need supplemental oxygen.

Can Anxiety Cause Low SpO2?

Yes, anxiety changes the way you breathe, which can also temporarily alter oxygen levels. Anxiety affects your fight or flight system, causing it to overdrive. This alters your respiratory rate and lead to shortness of breath, which may reduce your blood oxygen level. An episode of extended hyperventilation can cause carbon dioxide wash out, temporarily lowering oxygen levels.

Can Being Overweight Cause Low SpO2 Levels?

Obesity can affect your SpO2 levels. It contributes to sleep apnea, which affects the O2 levels. Obesity causes obesity hypoventilation syndrome (OHS), which reduces oxygen intake and ability to breathe deeply.

Obesity creates less efficient respiratory function than in a healthy individual. The extra weight, especially at the chest, requires the lungs to work harder for oxygen. The extra work results in an inadequate blood oxygen level in the brain, heart, and other major organs.

OHS develops directly from obesity with no other identifiable cause. Factors that contribute to its development or present themselves due to OHS include the following:

  • A body mass index (BMI) that measure more than 30.
  • The brain loses the ability to control breathing efficiently.
  • The respiratory system ceases to function properly.
  • Body parts can’t obtain enough oxygen.
  • Chronically low SpO2 levels result in functional body changes.

As awful as this may sound, OHS has a cure. Working to have a normal weight will treat the problem, according to Dr. Aiman Tulaimat, author of Obesity Hypoventilation Syndrome.

Do Smokers Have Lower SpO2?

Yes, smoking can decrease SpO2 levels somewhat in those who smoke regularly. It depends on how much a person smokes and their age. The body compensates for some of smoking’s effects, so some smokers exhibit normal saturation levels. The carbon monoxide (CO) in cigarettes and cigars binds in blood hemoglobin (Hg) similar to how O2 does, but with 200 times greater affinity. Essentially, it takes over, so your blood receives less O2, and your heart must work harder to distribute blood to your brain, limbs, and organs. The extra work the heart does results in a normal saturation level, but at a cost.

Another compensating factor comes when the blood produces more red blood cells (RBCs). More RBCs mean less plasma volume, which results in thicker blood. Thicker blood also takes more work for the heart to distribute.

A smoker can quickly reverse these adverse effects on their body by quitting smoking. In those who smoked for a long time, it takes about two weeks of no smoking to start reversing the damages. The positive changes take only a week to begin in those who haven’t smoked for very long.

Can Stress Cause Low SpO2?

No, normal psychological or work stress does not cause low SpO2 for a long time. When a person undergoes a traumatic experience that activates their fight or flight system, that may temporarily affect the SpO2. This only lasts for the duration of the event, such as fleeing a burning building. Since those types of things don’t happen daily, stress-related fluctuation occurs only occasionally and for a very short period.

During a particularly stressful event like a car accident, a person may breathe more shallowly than normal. Focusing on balanced breathing of five to six breaths per minute can help them calm down. Hyperventilating during a panic attack offers another example of the short duration of this type of fluctuation of SpO2.

Can Medications Affect Your SpO2 Level?

Some prescription medications can affect a person’s SpO2 levels. The use of illegal drugs and alcohol can do the same.

Some medications reduce the blood’s oxygen exchange ratio. If you feel tired when you’ve slept or feel shortness of breath, visit your doctor. That enables your medical practitioner to determine the reason for the problem and if it stems from low blood oxygen levels. It may not occur due to the medicine you take, but if it does, your doctor can switch your prescription, a quick and effective way to solve the problem.

Sometimes a prescription medication doesn’t cause the problem. Using illegal opioids or sedatives does. Recreational drug use can cause the same issue. Many illegal drugs depress the breathing center in the brain, which slows the body’s oxygen intake and breathing.

Finally, regular use or abuse of alcohol can inhibit normal breathing functions. Drinking close to bedtime or mixing alcohol with drugs can affect the body’s SpO2 levels. The alcohol inhibits the body from taking in sufficient oxygen, resulting in abnormal breathing.

Quitting illegal drugs or alcohol offers the only cure for this. Like other controllable development factors, such as obesity, an individual can stop using drugs and alcohol to reverse the damage to their body.

What Causes SpO2 to Drop for Short Periods?

Sometimes, a fault in the pulse oximeter causes an erroneously low pulse oximeter reading. A substance, such as nail polish on the individual’s fingernails, can block the reading or cause an incorrect reading. The oximeter might show SpO2 levels of 85% for a few seconds.

The finger oxygen meter or pulse oximeter uses the beer Lamberts law, which uses a small beam of light that the skin absorbs. The rest deflects from tissues and returns to the oximeter sensor.

So why might the oximeter show such a low value for a few seconds or moments?

  • A loosely attached probe can’t take an accurate reading.
  • Nail polish on the fingernails interferes with the measurement.
  • The probe was shaken during the measurement.
  • Other general technical issues affect the oximeter.

These things happen, and your doctor should conduct a second test to get a more accurate reading and try other tests, such as a pulmonary function test (PFT).

If you exhibit low readings of SpO2 consistently, this indicates a health issue unless you have asthma. Without a health problem, the typical person should measure a blood oxygen level of 95% to 100%. Consistent, too-low SpO2 can lead to the development of hypoxia, which requires oxygen treatment. The symptoms of hypoxia include the following:

  • Skin color change from blue to cherry red
  • Confusion
  • Persistent cough
  • Rapid breathing
  • Rapid heart rate or slow heart rate
  • Shortness of breath
  • Wheezing
  • Sweating

If you experience multiple symptoms, go to the minor emergency center or emergency room for treatment.

Injury can cause a temporary lowering of blood oxygen levels. The medical team often offers oxygen after an accident or getting injured during a sporting event. This keeps the SpO2 normal while medical staff administers treatment, alleviating one potentially major issue while dealing with other traumas.


Low SpO2 readings are a sign that something is wrong, and you should visit a medical practitioner to identify the problem. However, some factors can cause your SpO2 levels to fluctuate temporarily. It’s crucial to know what are the normal levels of oxygen saturation under different conditions, as well the tell-tale signs of low SpO2 levels, to determine whether you need immediate medical help. It’s worth investing in handy pulse oximeters, whether you have a respiratory contion or other health issues that affect your oxygen levels.