A pulse oximeter shows two main numbers: SpO2, an estimate of the percentage of oxygen in the blood, and PR, the pulse rate per minute. According to the US Food and Drug Administration (FDA), most healthy adults read about 95–100%. If your parent reads below 94% together with breathlessness, contact a doctor or hospital. If a repeat reading is 92% or lower, or they are so breathless they cannot finish a sentence, their lips turn blue, or they become drowsy or confused, call 1669 immediately. For parents with chronic lung disease, the doctor may set a lower target, and the doctor's target is the one to follow.
The little device many families bought during the COVID years often comes out of a drawer on the night Dad says he feels "a bit breathless". You clip it on his finger and the number jumps around; one reading looks alarming, the next looks fine. Then come the questions: which one do you believe, do you go to hospital now or wait until morning? This guide helps you read the device correctly from the start, know which numbers mean watching, which mean calling the doctor and which mean calling 1669, and recognise when the device is misleading you.
Quick answer
- The screen shows SpO2 (%), the estimated blood oxygen level, and PR, the pulse per minute, plus a waveform or bar showing whether the signal is clear
- Most healthy adults read about 95–100%; knowing your parent's own usual reading on a good day helps enormously
- Below 94% with breathlessness: contact a doctor or hospital · 92% or lower on a repeat reading, or too breathless to finish a sentence, blue lips, drowsiness or confusion: call 1669 immediately
- For parents with chronic lung disease, the doctor may set a lower target, such as 88–92%; follow the doctor
- For an accurate reading: remove nail polish, warm the hand, rest at least 5 minutes, keep still, and leave the clip on for at least 1 minute until the number settles
- Symptoms matter more than numbers; if your parent is breathless, drowsy or blue-lipped, do not wait for the device to confirm it
1. How to read a pulse oximeter: what is on the screen?
Most devices show three things: SpO2, pulse and a waveform or signal bar. Read all three before trusting the number, because the waveform tells you how reliable the reading is.
SpO2: estimated blood oxygen
This is the number marked with % or labelled SpO2. The device estimates it from light shining through the fingertip, so it is an approximation, not a blood test. Many families confuse it with the pulse because the two numbers sit close together, so check the label every time.
PR or BPM: pulse per minute
This number carries a heart symbol or the label PR or BPM. Compare it with your parent's usual pulse, and tell the doctor if it is much faster or slower than usual and accompanied by symptoms. Ask the doctor what pulse range suits your parent, since some medicines and heart conditions affect it.
Waveform or signal bar
Regular, rhythmic waves mean the device is picking up a good signal. A flat, broken or jerky waveform means a poor signal, and the number on screen should not be trusted yet. Some models show a PI value, the strength of the signal at the fingertip; a lower value than usual for the device often means cold hands or poor blood flow to the fingers.
2. Oxygen levels in older adults: what is normal, what needs watching, what is an emergency
There are three levels: about 95–100% is where most healthy adults sit; below 94% with breathlessness means contacting a doctor; and 92% or lower on a repeat reading, or danger symptoms, means calling 1669 immediately. Always read the numbers together with how your parent is.
About 95–100%: where most healthy adults sit
This figure comes from the FDA. If your parent has lung or heart disease, ask the doctor what their normal reading and target are. Then measure several times on days when they feel well and note it as their "baseline". When they are unwell, the family can see at once how far the number has moved.
Below 94% with breathlessness: contact a doctor or hospital
This threshold appears in the Home Isolation manual of Thailand's Department of Medical Services (2022). If you see it, let your parent rest, warm their hand and measure again correctly as described in section 3. If it is still below 94% and they are still breathless, contact their doctor or hospital for advice. Do not simply wait overnight without talking to anyone.
92% or lower on a repeat reading, or danger symptoms: call 1669 immediately
International guidance, such as that of the UK's National Health Service (NHS), advises seeking emergency help straight away if a repeat reading is 92% or lower, or if any of these symptoms appear, even when the number is not yet low:
- So breathless they cannot speak in full sentences
- Blue lips
- Drowsy and hard to wake
- Suddenly confused or not making sense
Parents with chronic lung disease
For parents with chronic obstructive pulmonary disease (COPD), the doctor may set a lower target than usual, such as 88–92%. A number that looks low for others may be exactly what the doctor intends for your parent. Equally, trying to push the number higher yourself is not something the family should do. Follow the doctor's plan in every case.
Ask the doctor to write your parent's target, and the numbers at which to call the doctor or 1669, on one sheet of paper kept next to the device. Everyone at home, including any caregiver, then uses the same criteria without guessing.
3. How to measure oxygen accurately, step by step
An accurate reading needs a warm hand, a clean nail without polish, a rested body and a hand that stays still throughout. Then wait for the number to settle before reading it.
- Remove nail polish, or choose a finger without gel or acrylic nails.
- Warm the hand by rubbing the hands together or holding your parent's hand for a moment; if they have just come out of a cold air-conditioned room, wait until the hand is no longer cold.
- Let your parent rest for at least 5 minutes.
- Rest the hand still on a table or lap, not dangling, and away from bright light such as sunlight or a lamp shining directly on it.
- Clip the device on the index or middle finger, with the fingertip pushed fully in and the nail facing up.
- Leave it on for at least 1 minute, until the number is steady and the waveform is regular.
- If the number still moves, read the middle value that appears most often, not the lowest or highest that flashes up for a second.
- If no reading appears within 30 seconds, try another finger.
- Write down SpO2 and pulse straight away, with the time and what your parent was doing before.
If your parent has a tremor, gently support their wrist on the table rather than asking them to hold the hand still themselves.
4. What throws readings off, and how to tell a faulty reading from a real problem
Readings can be off with cold hands, poor circulation, nail polish or artificial nails, hand movement, bright ambient light, smoking and darker skin, which the FDA has warned about since 2021. To tell the difference, check the waveform, repeat the reading correctly and always look at your parent's symptoms.
Factors that affect accuracy
- Cold hands or poor blood flow to the fingers, common in older adults, cold rooms or during illness; the device may read low or not at all
- Nail polish, gel or acrylic nails block the light the device uses
- Hand movement or tremor makes the number jump
- Bright ambient light interferes with the sensor
- Smoking can make the reading inaccurate
- Darker skin: the device may be less accurate than in people with lighter skin
Faulty reading or real problem?
- Low number, but your parent is chatting comfortably, looks normal and the waveform is irregular: usually a poor signal. Warm the hand, measure again and try another finger
- Low number, good waveform, and still low on several fingers: trust the number and follow the criteria in section 2
- Number looks fine, but your parent is breathless, drowsy or has blue lips: trust the symptoms and get help immediately
If you suspect the device is faulty, test it on a healthy family member. If it reads abnormally for everyone, change the batteries or replace the device.
5. Symptoms to watch alongside the number
The number is only part of the picture; your parent's symptoms tell you more. When symptoms and number disagree, trust the symptoms first.
Get help immediately for these signs, even if the device still shows a good number:
- Rapid breathing, severe breathlessness, noisy or obstructed breathing, or too breathless to speak in sentences
- Blue lips or fingertips
- Drowsiness, difficulty waking, or sudden confusion
- Sweating and cold skin
- Sudden, severe chest pain
In older adults, new drowsiness or confusion must always be taken seriously. Sometimes they do not say they are breathless, but they talk less, stop eating or call family members by the wrong name. For what to tell the dispatcher when calling 1669 and how to prepare your home in advance, see our emergency plan for older adults at home and calling 1669.
6. Keeping an oxygen log the doctor can use
A good record includes the time, SpO2, pulse, what your parent was doing beforehand, oxygen use and the flow rate prescribed, and symptoms at the time. How often to measure is for the doctor to decide.
Sample log
- Tuesday 07:30, resting after waking up, no oxygen in use
- SpO2 ..... % pulse ..... per minute, regular waveform
- Symptoms: slight cough, talking normally
- Tuesday 14:00, after walking to the bathroom, oxygen in use as prescribed
- SpO2 ..... % pulse ..... per minute, measured on right middle finger
- Symptoms: breathless after walking, better after a short rest
If the doctor also wants blood pressure readings, use the same notebook; see how to measure blood pressure accurately at home. Bring the notebook to every appointment so the doctor sees a trend over several days rather than a single reading in the consulting room.
7. Parents on home oxygen: what families need to know
Families must never adjust the oxygen flow rate themselves, whether the reading is low or high. Use it as the doctor prescribed, and if the number or symptoms change, call the doctor or follow the criteria in section 2.
- Write the prescribed flow rate on a card attached to the machine so everyone at home sees the same setting
- If the reading drops while oxygen is running, first check that the tubing is connected, not kinked or crushed, and that the machine is working, then measure again. If it is still low or your parent has symptoms, contact the doctor or call 1669 according to the criteria
- No smoking, lighters or open flames near the machine or tubing
- For parents whose doctor has prescribed home oxygen, KIN HomeCare rents a 5-litre oxygen concentrator for 2,200 baht per month (delivery in Bangkok and surrounding provinces); see medical equipment rental
Mistakes families often make
- Reading the number the moment the clip goes on. Early numbers are not yet stable. Leave it on for at least 1 minute and check the waveform before reading.
- Panicking at a number that flashes up for a second, and rushing out at night after measuring incorrectly, or the reverse, relaxing after one good reading. Repeat the measurement correctly and decide on the steady number together with symptoms.
- Trusting the number over symptoms. Your parent is breathless, drowsy or blue-lipped, but the family waits because the device still reads well. Symptoms come first.
- Adjusting oxygen yourself, raising or lowering the flow according to the number. Use it as prescribed and call the doctor.
- Not knowing your parent's usual reading, so you cannot tell how much today's number has changed. Measure and record a baseline on days when they are well.
When to bring in a professional team
If the doctor wants oxygen checked regularly, your parent has lung or heart disease that can change quickly, uses oxygen at home, or nobody is around during the day to watch for symptoms, having someone who measures on time and knows whom to alert helps the family not miss the moments that matter.
- Caregiver (nursing assistant): measuring vital signs and keeping records is a daily routine. The caregiver measures at the times set by the family and doctor, records readings and symptoms truthfully, and alerts the family when readings or symptoms reach the agreed criteria. A 12-hour shift is 1,800 baht per day (3-day minimum) or 30,000 baht per month (one day off per week); a live-in 24-hour caregiver is 2,500 baht per day. To have a caregiver take and log readings for a short period before committing long-term, start with 3 days of daily hire, or one week at 12,000 baht (12-hour shift) or 16,000 baht (24-hour live-in). See elderly care at home.
- Registered nurse: for parents with complex needs, several conditions, or who need close clinical assessment. A 12-hour shift is 3,500 baht per day or 90,000 baht per month, or a nurse home visit is 1,800 baht per visit. See home nursing. If you cannot decide between a caregiver and a nurse, read home nurse versus caregiver costs compared.
Frequently asked questions
What is a normal pulse oximeter reading?
Most healthy adults read about 95–100%, according to the FDA. If your parent has lung or heart disease, ask the doctor what their normal level and target are, and record readings on good days for comparison.
What should an older adult's oxygen level be?
Start from the same range as other adults, about 95–100%. For older adults with chronic lung disease, the doctor may set a lower target, such as 88–92%, and the doctor's target takes priority.
What oxygen level means going to hospital?
Below 94% with breathlessness: contact a doctor or hospital. If a repeat reading is 92% or lower, or your parent is too breathless to finish a sentence, has blue lips, or is drowsy or confused, call 1669 immediately. Avoid driving them yourself if they are seriously unwell.
How do I read a pulse oximeter, and which number is oxygen?
The number marked % or SpO2 is oxygen; the number with a heart symbol or labelled PR or BPM is pulse. Before reading, check that the waveform is regular and wait at least 1 minute for the number to settle.
Why does the reading keep changing, and differ between fingers?
Usually cold hands, movement, nail polish or bright light. Warm the hand, rest, keep still and measure again. If it still moves, read the middle value; if no reading appears within 30 seconds, change fingers.
Are fingertip pulse oximeters accurate?
Accurate enough to track trends at home when used correctly, but the reading is an estimate, not a blood test. Cold hands, nail polish, movement, bright light, smoking and darker skin can all affect it, so always check symptoms too.
What kind of pulse oximeter should I buy?
One with a large, easy-to-read display, a waveform or signal bar, a clip that fits your parent's finger, and sold as a medical device. The brand matters less than measuring correctly.
Talk to the KIN HomeCare team
If your parent needs regular oxygen checks, uses oxygen at home, or the family is not confident about reading the numbers and deciding in time, tell the team about their symptoms and daily routine. We will help you decide between a caregiver and a nurse, and which shift to start with.
- Call 061-881-9399 (+66 61 881 9399) for elderly care, nursing and equipment rental
- LINE @KINHOMECARE
- Free consultation: the team helps you work out which service fits before you decide
- Home care available nationwide
This information is general guidance for families and does not replace advice from your parent's doctor.
Prepared by the KIN HomeCare team · Prices as of September 2026; please confirm with our staff before booking.
