Buying a Peak Flow Meter for Asthma: A Guide
Buying a peak flow meter for asthma: what to look for, how to get one, how to measure, and what a pulse oximeter can and cannot tell you.
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A peak flow meter was recommended to you, or you wonder whether a pulse oximeter belongs on your list too. In short, the NHS says you may be given a meter on prescription or advised to buy one. Someone should teach you to use it. A pulse oximeter has clear limits, because the FDA says many are not reviewed for clinical decisions. Peak flow numbers stay on paper, since Sam does not record them. Next to them, the asthma diary in Sam logs reliever uses apart from your preventer schedule. Its doctor report comes out as a PDF once you confirm a doctor diagnosed your asthma. That is general information, not medical advice.
Whether a device is useful for you is your doctor's call. This text recommends no brand and compares no prices.
Do you even need a peak flow meter?
Not everyone does. The NHS says a peak flow test measures how quickly you can blow air out of your lungs, and it is used to help diagnose and check asthma. Asthma + Lung UK is blunter: healthcare professionals do not always recommend home monitoring, because for some people watching symptoms is the better way.
A meter helps most in particular situations. Asthma + Lung UK lists recovering from an asthma attack, a recent change to your treatment plan, and symptoms that are hard to control. Outside those, measuring every day can add little. Ask your doctor or asthma nurse whether it is worth it for you, and how often to check.
Whatever you decide, your written asthma action plan is the thing that matters most, not the device. The plan tells you what to do when symptoms or your peak flow change.
What to look for when you choose a meter
There is no single best meter, and this text names no brand. This checklist is our own summary, not an official standard:
- A scale that fits you, in litres per minute (l/min).
- A clear pointer or display that you can reset.
- A mouthpiece you can clean.
- A version for a child, with a smaller mouthpiece and a lower scale, if you buy for one.
- A setting that your doctor or asthma nurse can show you on your specific device.
Asthma + Lung UK adds two practical points. Use the same meter every time, because a different one can give slightly different scores. And clean or replace it regularly, because meters become less accurate over time and with frequent use. The leaflet that comes with your meter tells you how to clean it.
How do you get one?
In the UK, the NHS says you may be given a meter on prescription from your GP or asthma nurse. Asthma + Lung UK adds that you can also buy one yourself from a pharmacy or online. In the US, ask your doctor or pharmacist which meter to buy; some are sold in pharmacies and online. Whatever the route, the key step is the same: ask a professional to show you how to take a reading and what your scores mean for you.
If you buy for a child, choose the child version. Asthma + Lung UK says a child's meter has a smaller mouthpiece and a lower scale. Which device works for your child is best settled with your doctor or asthma nurse.
How do you measure correctly?
The method is consistent across the NHS and Asthma + Lung UK. Sit or stand upright, and use the same position each time. Reset the pointer. Breathe in deeply, seal your lips around the mouthpiece, and blow as hard and as fast as you can. Do this three times with a short rest between, and record the highest score.
Asthma + Lung UK adds the habits that make the record useful. Measure at the same times every morning and evening. Use your best effort each time. Use the same meter every time. And keep a diary, writing down symptoms and what you did that day, such as exercise or when pollution was high.
Note which medicine you took before measuring. That detail, plus your symptoms, helps you and your doctor read the pattern together.
How do you read your own scores?
The main thing is your personal best, the score that is usual for you when you are well. Asthma + Lung UK says you need to record for at least two weeks to find it, and to ask your GP to check it again if it was set years ago or you change meters.
Your doctor explains what changes to watch for and writes this into your action plan. A drop below your best can be an early sign your asthma is getting worse. But your symptoms count as much as the number: Asthma + Lung UK says to act when you have symptoms even if your peak flow is normal.
A sudden low score or any sign of an asthma attack is not a topic for a buying guide. Follow your action plan, and for severe breathing trouble call your local emergency number (112 in the EU, 999 in the UK, 911 in the US).
Is a pulse oximeter useful for asthma?
A pulse oximeter clips on a fingertip and estimates blood oxygen and pulse rate. It sounds useful, but it has clear limits, and the FDA is explicit about them.
The FDA, the US regulator, says many pulse oximeters are sold as wellness or sporting products and are not reviewed for use in clinical decisions or in deciding whether to seek medical care. Accuracy can be affected by poor circulation, skin pigmentation, skin thickness, skin temperature, smoking, and nail polish.
That does not mean the device is useless. It means a single number is not the same as clinical judgement. For asthma, your symptoms and your written action plan carry the weight, not a finger clip. If you own one, note your symptoms alongside the reading. Follow your doctor's advice on when to use it. Ask whether it adds anything for your case.
What does measuring not replace?
Every person with asthma should have an individual asthma action plan. The CDC says everyone with asthma needs their own plan, written with their health care provider. From that plan come the green, yellow and red zones, where your peak flow relative to your best tells you what to do.
A meter is a tool inside that plan. It does not replace your inhalers, your preventer schedule, or the plan itself. Your preventer times and intake can be ticked off in the medication list in Sam. If you log peak flow values, they stay in your own record and in your peak flow diary. In Sam you keep the reliever uses, night waking, and attacks that the numbers alone never show.
Log what the meter cannot show, and take it to your review
Your peak flow record holds numbers. Sam holds how the week actually felt, so the two belong together at your appointment.
- Reliever puffs, night waking and attacks go into the asthma diary apart from your preventer schedule, instead of living only in your memory.
- Air quality and pollen for the day sit with entries made today when you share your location, which a paper meter cannot add.
- The doctor report (PDF) summarises the period you choose, so you bring your own record rather than trying to remember it.
Peak flow values themselves are not entered in Sam. The limit is simple: the diary records what you experience, while the meter stays in your own record.
Try Sam HealthSam is a wellness companion, not a medical device. The app does not diagnose, treat, cure or prevent any condition or health state. Always consult qualified professionals for medical decisions.
Related reading
- Asthma diagnosis: what now, your first weeks
- Asthma not controlled? What that means
- Asthma symptoms: overview, diary and doctor visit
- Respiratory rate, sleep and asthma with Apple Health
- Asthma and the Military, Fire Service, Police
Sources
Updated: October 2026
- NHS: Peak flow test (last reviewed 3 March 2026)
- Asthma + Lung UK: Peak flow test (last reviewed 30 June 2026)
- Centers for Disease Control and Prevention: Living with asthma (last reviewed 28 August 2026)
- FDA: Pulse oximeter basics (content current 26 March 2025)
More on Asthma
Frequently Asked Questions
Can a peak flow meter tell me if I have asthma?+
Not on its own. The NHS says a peak flow test may be done alongside other tests, and a doctor or nurse reads a pattern of scores together with your history. A meter alone is not a diagnosis.
Do I need a prescription to get a peak flow meter?+
Not always. The NHS says you may be given one on prescription or buy one from a pharmacy, and in the US you can ask your doctor or pharmacist which meter to get. Either way, someone should teach you to use it first.
How often do I measure peak flow at home?+
It depends on why you measure. Asthma + Lung UK says if you check at home, take it at least twice a day, every day, at similar times. Your doctor or asthma nurse sets the rhythm that fits you and writes it in your action plan.
Why does my new meter give different numbers than the old one?+
Different meters can give slightly different scores. Asthma + Lung UK says to use the same meter every time and discuss a change with your professional. If you switch meters, you may need a new personal best score.
Is a pulse oximeter useful for someone with asthma?+
It has limits. The FDA says many pulse oximeters are wellness products that are not reviewed for clinical use or deciding whether to seek medical care. A reading is not a substitute for symptoms or your action plan, so ask your doctor if one adds anything for you.
Which peak flow meter is the best one?+
There is no single best model. Asthma + Lung UK and the NHS focus on technique and consistent use, not on a brand. Ask your doctor or nurse which device fits you and to show you how to use it.
What should be in my peak flow record?+
A diary with date, time, the highest of three blows in l/min, and which medicine you took before measuring. Asthma + Lung UK also suggests noting symptoms and what you did that day. You bring the diary to your review.