Blood Oxygen Saturation
Blood Oxygen Saturation (SpO2) measures the percentage of haemoglobin in your blood carrying oxygen. Your organs — especially the brain and heart — need a constant, adequate supply of oxygen to function. Normal healthy adults have SpO2 of 95–100%. Even a small drop below 92% can significantly impair cellular function and mental clarity.
Normal range
How Vsense measures it
Vsense estimates SpO2 using the rPPG signal from your facial scan — analysing how different wavelengths of light are absorbed by oxygenated vs deoxygenated haemoglobin in your skin. For precision, a fingertip pulse oximeter provides clinical-grade readings.
How it's scored
98–100%: Excellent. 95–97%: Normal range. 92–94%: Below normal — consider medical evaluation especially if symptomatic. Below 92%: Low oxygen — seek medical attention. Below 88%: Medical emergency.
What a high reading means
SpO2 cannot exceed 100%. Very high readings (above 100%) from any device are measurement artefacts. A reading of 99–100% is ideal.
What a low reading means
SpO2 below 95% is below normal. Below 92% is concerning and may indicate lung disease (COPD, pneumonia, asthma), sleep apnea, heart conditions, anaemia, or altitude exposure. Symptoms of low SpO2 include shortness of breath, confusion, rapid heart rate, and bluish lips or fingernails (cyanosis).
How to improve it
Exercise
- Aerobic exercise strengthens your heart and lungs, improving oxygen delivery efficiency over time
- Deep breathing exercises (diaphragmatic breathing) maximise lung volume and oxygen uptake
- Swimming and yoga breathing are excellent for improving respiratory capacity
- At high altitude: gradual acclimatisation — ascend slowly and allow 1–2 days to adjust per 1,000m
Diet
- Iron-rich foods (spinach, lentils, red meat, pumpkin seeds) are essential for haemoglobin production — anaemia lowers SpO2
- Vitamin C (citrus, bell peppers, broccoli) significantly improves iron absorption
- Vitamin B12 (meat, eggs, dairy, or supplement if vegan) is critical for healthy red blood cells
- Folate-rich foods (leafy greens, beans) support red blood cell production
- Stay hydrated — dehydration affects blood volume and oxygen transport
Lifestyle
- Quit smoking — smoking destroys lung tissue and binds carbon monoxide to haemoglobin, directly reducing SpO2
- Avoid indoor air pollution — ensure good ventilation and check for carbon monoxide if SpO2 is consistently low
- Sleep on your side rather than your back — back sleeping worsens sleep apnea and can lower overnight SpO2
- Treat allergies and sinusitis — nasal congestion reduces oxygen intake during breathing
- Practice nasal breathing — the nose warms, humidifies, and adds nitric oxide to inhaled air, improving lung oxygen uptake by up to 18%
Natural remedies
- Pursed lip breathing (inhale through nose, exhale slowly through pursed lips over 4–6 seconds) immediately increases SpO2 in people with lung conditions
- Diaphragmatic breathing: lie flat, hand on belly — breathe deeply so belly rises, not chest — maximises lung base ventilation
- Ginger tea has mild bronchodilating properties and may ease breathing
- Chlorophyll-rich green juices (wheatgrass, spirulina) support haemoglobin production
Frequently asked questions
What is a dangerously low oxygen level?
Below 90% SpO2 is considered dangerous and requires immediate medical attention. Between 90–95% is concerning and warrants medical evaluation, especially if accompanied by symptoms like shortness of breath or confusion.
Can SpO2 drop during sleep?
Yes — SpO2 can drop during sleep, especially in people with sleep apnea. Normal drops are less than 3–4%. Significant drops (below 90%) indicate sleep-disordered breathing that needs medical attention.
Does altitude affect oxygen levels?
Yes. At high altitudes, lower atmospheric oxygen means SpO2 naturally decreases. At 2,500m above sea level, SpO2 of 92–95% is normal. Most people fully acclimatise within days to weeks.
Is 96% SpO2 normal?
Yes, 96% is within the normal range (95–100%). Optimal is 98–100%. If you're consistently reading 95–96%, it's worth monitoring and discussing with a doctor, especially if you have respiratory symptoms.
Can anaemia affect oxygen saturation?
Anaemia reduces the amount of haemoglobin available to carry oxygen, but SpO2 measures what percentage of available haemoglobin is saturated — so mild anaemia may show normal SpO2 while the actual oxygen delivery to tissues is reduced. This is a limitation of SpO2 monitoring.
How does smoking affect oxygen levels?
Smoking damages lung tissue and reduces its ability to transfer oxygen. It also introduces carbon monoxide, which binds to haemoglobin 200× more strongly than oxygen, directly displacing it. Long-term smokers often have chronically lower SpO2 and reduced exercise tolerance.
