What does it mean if I consistently get blood oxygen readings in the low 90's on my Apple Watch, could I have an issue with my lungs?

Apple Watch Low Oxygen Readings: Clinical Significance

If your Apple Watch consistently shows oxygen saturation readings in the low 90s, this warrants medical evaluation with proper pulse oximetry and potentially arterial blood gas testing, as consumer smartwatches have significant accuracy limitations and cannot reliably diagnose lung disease, but persistent low readings may indicate underlying cardiopulmonary pathology that requires professional assessment.

Understanding the Accuracy Limitations

Apple Watch Measurement Reliability

• The Apple Watch Series 6 shows strong correlation with medical-grade pulse oximetry in controlled settings (r = 0.89), but this does not mean it's clinically reliable for diagnosis 1, 2
• A significant proportion of measurements are either unsuccessful or incorrect, particularly in patients with respiratory distress who cannot remain still during measurement 3, 4
• Studies show the Apple Watch incorrectly classified approximately 23% of patients regarding hypoxia status, with 11% falsely reassured they were not hypoxic when they actually were 5
• Tachypneic patients (rapid breathing) require multiple measurement attempts, reducing reliability 2

Why Consumer Devices Fall Short

• The Apple Watch requires patients to remain in a stable, motionless position for accurate readings—difficult when experiencing respiratory symptoms 4
• Movement artifact, poor probe positioning, and respiratory distress all lead to inaccurate measurements 6
• These devices are not FDA-approved medical devices and should not be used for clinical decision-making 3, 4

What Low 90s Oxygen Saturation Actually Means

Clinical Context Matters

• Normal oxygen saturation is 94-98% for most healthy individuals at sea level 6
• Readings consistently in the low 90s (90-93%) represent mild hypoxemia that may indicate underlying cardiopulmonary disease 6
• However, certain chronic conditions have different target ranges: patients with COPD, cystic fibrosis, or chronic respiratory failure may have target saturations of 88-92% 6, 7

When to Seek Medical Attention

You should obtain professional medical evaluation if:

• Oxygen readings are consistently below 94% in someone without known lung disease 6
• You experience shortness of breath, chest pain, rapid breathing (>30 breaths/min), or altered mental status 8
• Readings are accompanied by symptoms such as breathlessness on minimal exertion, chronic cough, or exercise intolerance 6

Proper Medical Evaluation Pathway

Step 1: Verify with Medical-Grade Equipment

• First, confirm readings with a medical-grade pulse oximeter before drawing conclusions 6, 9
• Medical pulse oximeters have accuracy within ±2%, far superior to consumer devices 6
• Reposition the probe and repeat measurements if initial readings seem abnormal 6

Step 2: Clinical Assessment

If medical-grade pulse oximetry confirms low saturations:

• Arterial blood gas (ABG) measurement provides definitive assessment of oxygenation and can detect hypercapnia (elevated CO2) 6, 7
• Spirometry should be measured to confirm or exclude airflow obstruction, particularly in patients over 50 who are long-term smokers 6
• 12-lead ECG should be obtained to exclude cardiac causes of hypoxemia 8

Step 3: Risk Stratification

Your physician will determine if you're at risk for hypercapnic respiratory failure (CO2 retention), which changes management:

• Risk factors include: COPD, morbid obesity, cystic fibrosis, chest wall deformities, neuromuscular disorders 6, 7
• These patients require blood gas monitoring within 30-60 minutes of any oxygen therapy changes 6, 7

Common Pitfalls to Avoid

Don't Self-Diagnose Based on Smartwatch Readings

• Consumer devices cannot replace medical evaluation for persistent low oxygen readings 3, 4, 5
• Even the most accurate smartwatch (Apple Watch with external device) misclassified nearly 1 in 4 patients regarding hypoxia 5

Don't Ignore Symptoms

• Oxygen saturation alone doesn't tell the whole story—respiratory rate, heart rate, blood pressure, and mental status are equally important 8
• A patient can have "normal" oxygen saturation but still be in respiratory distress requiring urgent intervention 8

Don't Delay Evaluation for Chronic Symptoms

• If you have chronic breathlessness on minor exertion (like walking on level ground), this warrants spirometry and full pulmonary evaluation regardless of oxygen readings 6
• Long-term smokers over age 50 with unexplained breathlessness should be evaluated for COPD 6

Bottom Line

Your Apple Watch readings in the low 90s are a signal to seek proper medical evaluation, not a diagnosis. The device's limitations mean you cannot reliably determine if you have lung disease based on these readings alone. Schedule an appointment with your physician for medical-grade pulse oximetry, and if confirmed low, proceed with arterial blood gas testing and spirometry to identify any underlying cardiopulmonary pathology 6, 1, 2.