Blood Oxygen Log

Track and monitor your blood oxygen saturation (SpO₂) and pulse readings over time. Log values from your pulse oximeter, tag context (rest, exercise, sleep), and visualize trends.

Create a profile to start logging

About Blood Oxygen Log

Blood Oxygen Log is a free, private SpO₂ tracker that runs entirely in your browser. Pair it with a fingertip pulse oximeter, smartwatch, or any device that reads oxygen saturation, and use this log to record your readings over days, weeks, and months. Tag each reading with context (at rest, after exercise, during/after sleep, or random) so dips and spikes can be interpreted correctly. Useful for people with COPD, asthma, sleep apnea, recovering from respiratory illness, exercising at altitude, or anyone who simply wants to keep an eye on respiratory health. Multiple profiles support tracking the whole family from one device. All data stays in your browser via IndexedDB — nothing is ever uploaded.

Blood Oxygen (SpO₂) Reference Ranges

Normal

95–100%

Mild Hypoxemia

91–94%

Low (Concerning)

86–90%

Critical

Below 86%

Reference ranges based on common clinical guidelines. People living at high altitude or with chronic lung disease may have a personal baseline below 95% — always discuss your numbers with your healthcare provider.

How to Use the Blood Oxygen Log

  1. Create a profile for yourself or a family member.
  2. Take a reading with a pulse oximeter — sit still for 30 seconds, warm hands work best, and skip nail polish.
  3. Click Add Reading and enter your SpO₂ % and (optionally) pulse.
  4. Choose the context — at rest, after exercise, during/after sleep, or random.
  5. Add optional notes (e.g. "after climbing stairs", "during cold").
  6. Use the context filter and date range to focus on patterns.
  7. View the trend chart — points are color-coded by category, with pulse on a secondary axis.
  8. Export your data as CSV to share with your doctor.

Frequently Asked Questions

Is my data private?

Yes. All readings are stored locally in your browser using IndexedDB. Nothing is sent to any server. Clearing browser data permanently removes the log — export to CSV regularly for backup.

What is SpO₂?

SpO₂ (peripheral capillary oxygen saturation) is the percentage of hemoglobin in your blood that is carrying oxygen. A pulse oximeter shines light through your finger to estimate it. Healthy adults typically read 95–100%.

When should I be concerned?

A single reading below 95% is rarely a worry — sensor fit, cold fingers, and motion all cause false dips. Persistent readings below 92% at rest, especially with shortness of breath or chest pain, warrant a call to your doctor. Below 88% sustained, or any reading below 85% with symptoms, is an emergency.

Why does my pulse oximeter give different numbers each time?

Cold hands, nail polish, dark skin, motion, low battery, and poor circulation all reduce accuracy. Sit still, warm your hand, remove polish, and wait 30 seconds for a stable read. Trends across many readings are more useful than any single value.

Why does context matter?

SpO₂ naturally drops during heavy exercise and during deep sleep. Tagging context lets you compare like with like — a 92% after a hard workout is normal, but 92% sitting at rest may not be.

Can I track multiple people?

Yes — create one profile per person. Switch between them in the sidebar. Readings stay separate and the trend chart updates per profile.

Does this replace a pulse oximeter?

No — this tool only logs and visualizes readings. You still need a pulse oximeter or compatible smartwatch to measure SpO₂.