Asthma UK community forum

Any help on how to understand peak flow readings?

Hey i am new here and tried looking through all the threads to make sure that no one has asked this question before, and as far as i can see they havent so i hope its ok that i ask this.

I am 21 and 5.7 inches tall and my best peak flow when i went to the doctor was 450.

I only got diagnised with asthma about 3 weeks ago and went again to my asthma nurse yesterday to finalize my meds and put them on repeat.

now while i was there she measured my peak flow and it was 350 and she said ""oh last time it was 450"" and i said ""i think its the cold"" which she nodded to.

now my question is: is there a big difference between the two readings? and if so then how big? and what does it mean? was it the cold? or is it because i havent been taking my brown inhaler in the past week because i was going through denial?

im so sorry guys for all the babble and stuff in this post. im just lost and confused and dont know who to talk about it with :(

8 Replies

Hi there, I could ask that same question myself. Diagnosed with asthma just this year, I'd Clenil Modulite for the first months then as I wasn't really improving plus the Clenil gave terrific leg cramps, I was changed over to Seretide 125 and that's when I got the peak flow meter. At first it looked like an earthquake reading but never got more than 300. Singulair added last month to see if that would help - it hasn't and I now have the added pleasure of either being wide awake all night as if it was the middle off the night or I fall asleep and have nightmares. Great fun, not.

So yes I'd love to know what the different readings mean and why when the readings don't change and stay at 280 over several days with no ill-effects, it actually means the asthma is not being controlled.

Moira xx

Nipping off to see if I cen get a decent nights sleep - not had any singulair tonight and not taking eve n now.


aaaw that sounds awful! Im just on ""salamol"" (?) for now and a brown inhaler and have had a couple of leg cramps in the night. never occurred to me it could be the inhalers??

Hope you slept better last night! I had an attack so not much sleep going on there for me.. I feel weak and tired today too- is that normal after a flare up to feel unwell for a day after?

hoping someone will come along and shed some light on the PF questions!




Hi Lizzie, and welcome !

Considering a predicted peak flow for you is 435, based on age, sex and height (assume you meant 5ft 7), but anything down to 350 would still be considered within normal range, you obviously have very good peak flows. Yes colds and cold weather can reduce the value, but not taking your inhaler doesn't help.

Question, you had a peak flow of 450 at the time of diagnosis? Before being prescribed any medication.

I don't know if you have peak flow meter to record your figures daily, but if so, don't worry about the actual figures, the pattern from them is more important, and obviously no symptoms such as cough, tight chest, breathlessness etc.



Over the years I have had many forms of medication and the leg cramps got terrible. Finally this year the consultant presciribed Quininne and it works. Only drawback is my repeats are now nearly on two full pages. As I get older the list gets longer. Luckliy I have a pre paid cettificate by direct debit. Get onto your MP's to get teh prescription charges debacle sorted out

Peter S - aka Grumpy Old Man (GOM)


hey chris.

yes sorry i meant 5 ft 7 lol.

No, the 450 was after i was on the blue and brown inhaler for one month. i dont know what my PF reading where when i was first diagnosed, because i had no idea what a PF was in the first place and didnt look at the numbers.

however i did a test with not a PF reader but something else that was hooked to a pc? and then was given a couple of puffs from the blue inhaler and did the test again 20 mins later and my reading where better so they diagnosed asthma. but as i said i dont know what those readings where. so then i was given a blue inhaler and a brown one and one month later went back and because my symptoms had almost dissapeared i was confirmed to have asthma for sure. then 3 weeks later i went back (last friday) and had another reading and that was the 350 one.

sorry about the long post! im still trying to work things out!!!

i will tell you all something interesting though!! the very first day i went to the doctors about it all, i did my first PF ever and she told me i wasnt doing it right. i tried three times and all three times it was around 200. my lungs were killing me and i felt i literally could not give her a higher reading. she said again (the doctor that is) that i was doing it wrong, so she made me an appointment to see the asthma nurse a week later to do the computer test thing.

it occurs to me now, that maybe i WAS doing it right? and that i was actually just really unwell that day? because if my personal best is 450 when on medication then 200 is not good is it?

sorry again for the long posts!! i cant believe i have finally found people to talk about this with!!




HI Lizzie,

Good job, as I didn't think 5.7 inches was all that high lol!

The test you had was a spiromitry, the exact figures are not what's being looked at, they're important, but it records a graph of the blow, and the shape of the graph indicates asthma, COPD, or other possible lung conditions.

The two tests 10-20 mins apart show reversible air way obstruction, which is what your tests showed, an the shape of the graph indicated asthma.

A peak flow of 450 is good (for you), and ideally you should be able to now keep that peakflow within 20% of that figure, so 360 would be you 80% level.

You may have a peak flow meter to record your own readings daily, and if you keep getting reading below 80% of your best, that's an indicator your asthma isn't being controlled, don't worry though, something else can be added to help, and should go back and have a chat to your GP.

Yes 200 isn't good, that's less than 50% of your best, and when you get to understand how to manage your asthma, you'll realise that's not a good figure.

If you order this from the site, it will hopefully answer you questions better.

Also these may be of help





p f

I'm a nurse and I don't understand peak flows. Mine are always good around 450-500 but the wheeze I sound like a train chugging away, my doctor changes my medications on the sound I make because my peak flows are that good.You should carry on with the preventor though you don'nt think they are doing any good but beleive you me they keep that nasty asthma at bay.


I would guess that if it has dropped when you stopped your brown preventer inhaler then that is probably why!

I find that I can take less preventer at certain times of year than others. I rarely take my ventolin but whenever tempted to stop my reliever......peak flow drops after a few days and asthma symptons return.


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