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Peakflow Variation?

Hi all,

I'm new to this, and just wanted to check what is a ""normal variation"" when it comes to peak flow? All the information I read says that healthy people will have some variation, so what is acceptable?

For example my max is 460, but today I'm blowing 400 and the other day when I had chest tightness I was getting 380. No major dips I know, but are they considered ""normal""?

5 Replies

Hi there I think that's quite a big ""normal"" variation and signifies your asthma is not as well controlled as normal. Mine only varies from bout 420 - 450. I would there thought it would be worth maybe up'ing your steroidal inhaler if you take one for a few weeks and keep monitoring your PF?


Thank you so much for your reply - it really helps to know what sort of numbers I should expect. I feel like I've suddenly entered a very confusing world with all this peak flow business!

At present I've just been prescribed a salbutamol inhaler for use before exercise, but my doc has said I can use it at other times if I feel tight chested. I've been advised to book an appointment with the asthma nurse as well, but they're fully-booked at the mo.

I've had a strange few days, not really sure what is wrong - I suspect a virus, although I don't really have any obvious cold symptoms except maybe a bit of throat discomfort a few days ago. Chest has been heavy though, and I've been getting night time ""whistling"" where my PF drops to 340. After inhaler it bounces back to 410-440 and the whistle disappears.

I feel a bit reluctant taking my inhaler when I don't really know for certain if I should be, as I've had no official diagnosis. I also don't feel I can go back to my doc yet as I've not actually done what she's asked yet - which was to monitor PF in relation to exercise - as I've not done anything but eat too much food and laze about over the Christmas period lol.



Like a lot of things to do with asthma, peak flow can be highly individual and in time you will come to learn what is normal for you. 460 to 380 is quite a big variation but what is important is using it with other factors so being symptomatic at the time is key. It is also worth looking for patterns - mine is a lot lower in the morning than evening which is quite typical of asthma. If you are not already, it might be worth recording more than just numbers for a while. Although it was quite time consuming, I recorded my peak flows whenever I was sympomatic, before and after taking my reliever and included information like symptoms, location and what I had been doing. This was really useful when discussing my asthma and how to control it with my consultant over the summer. After only a few weeks, we could piece together that yes my reliever was working (there was a question whether it was asthma despite having asthma for over 25 years) and make a very strong link to hayfever.

If your inhaler is working in relieving symptoms and bringing your peak flow up then I would certainly continue to take it as required. I would also make a note of this to take to the asthma nurse when you see them. Although it is a bit of a pain for a few weeks, it really does help then (and you) to build up a picture of your asthma which really helps when trying to control it.


Hi MissingSilence :)

I've only suffered from asthma for about a year, so by no means an expert, but I'm going to second what both KaylaCP and MammaMia said. It's really important to give the drs/nurses a good picture of what is going on with your asthma and the peak flow is a good way to do that. To be in the green zone (ie where you are getting good control of your symptoms) your PF needs to be 80% or above your personal best (so for you that's 370 and above). If your PF is dropping between 370 and 230 you are in the amber zone and need to see a dr/nurse as they need to review your asthma control. So yours going down to 340 and you needing the blue inhaler when you're not exercising means it's a good idea to have a chat with someone and possibly introduce something else to help prevent chest tightness. You should ideally be recording your PF first thing in the morning and between 4pm and 7pm at night. That's because the natural levels of steroids in the body are at their lowest in the morning and at their highest between 4 and 7pm. This will give the medics a good sense of how your body or any medication you are taking are handling your symptoms and if you need to go up a step or down a step in terms of medication.

Having said all that, I am an anomaly in that my lowest ever recorded PF is only 80% of my PB and yet I feel totally rubbish following a virus and needing to take a short course of steroid tablets! Looks like I'm getting a referral as one of the nurses is unsure of my diagnosis because of this, even though I have very classic symptoms/reactions. Hey ho.

Hope you start feeling better soon!


It all usually works around your personal best peak flow. I have heard different numbers to Aylab. In hospital they like PF to be over 75% for discharge! and I gather than my green zone is my top 25%, and then below 50% most people need to see a doctor or go to A&E, (if after nebs I'm still below 50% they'll do more treatment etc) so that's the kind of variation you're expecting!

Some people get very little variation even when very symptomatic, some get loads without ever really feeling much so you'll get used to what your peak flows do!

Salbutamol is a fairly harmless drug for most people, so don't be too afraid to take your inhaler if you're struggling. If you're in doubt and don't want to take salb but think you might need to you could always ring 111 and get some advice?? If I'm unsure what I need to be doing we my steroids and can't get hold of my GP then I ring 111 and you can get through to a GP who can advice!


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