British Lung Foundation

I need help understanding FEV1/FVC

I was diagnosed with mild COPD a year ago. I've just had my third spirometry test. My FEV1 is still in the normal ranges but has declined by 6% over a years time. My FVC has declined by 12% over a years time but still in the normal ranges also. I brought up this decline to my nurse and she stated that the only number they look at is the FEV1/FVC number which has remained the same over a years time. Is this accurate? Should this be the only number to consider in these tests? I was under the impression that any decline in FEV and FVC was not good. Even if in the normal ranges. Thanks in advance for any help anyone can give me.

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28 Replies

My FEV1 drifts up and down over time so it's not really a constant. It can change from day to day.

Thank you so much for your reply. I'm still trying to learn it all.

Hi I think you are getting a bit confused here. If you have been diagnosed with COPD then your levels are not in the normal range but in the COPD range. You will be diagnosed mild if your level is over 70% but under 80%. I have just gone into the moderate range at 66% from the mild.

FVC is how long you can blow out for on a peak and flow meter and your FEV1 is how much you can blow out in 1 second. I don't know my FVC but my FEV1 is 66%. So this figure is to my mind the most informative one.

Puff is right though that FEV1 levels can vary at any given point usually only by a few points. For example it is very unlikely you will go up or down more than 10 points or so.

These are only numbers though and it is how the disease affects you which is important. Two people with the same figures can vary enormously. x


Thank you so much cough a lot!

All of my numbers are in normal range with the exception of my FEV1/FVC which is 72. For my age, heighth and weight it should be in the 80's. This is what brought my doctor to my diagnosis of early COPD.

What concerned me on this last test was that some numbers were decreased. Though FEV1 and FVC were still in normal ranges they were down some percentages. I'm planning on getting a second opinion because my current doctor does not explain things well.

Thank you so much again for your input!

You are welcome suzipete. Glad I was able to help a bit. x

If FEV1 has declined by 6% and FVC has declined by 12% then FEV1/FVC has not stayed the same, it's increased.

An FEV1/FVC ratio greater than or equal to 0.7 is in the normal range.

Thank you still truckin! You are absolutely correct. The FEV1/FVC went up 1 point (73).

From my understanding for my age (37) my Fev1/FVC should be .80. Since its decreased they classify me as mildly obstructed COPD.

Thank you so much for your input!

Hi Suzipete,

This isn't going to be helpful as I'm still confused though I have what I thought was a basic grasp of the terms and figures. My FEV1 % is 95 and I was told by a specialist a few days ago that I have moderate that throws all the theories I thought I understood out the window! 37 seems very young to have COPD I hope you are keeping well. Suz x

Hi Suz! Thank you for your comment! Yes that is surprising that you'd be moderate with a FEV1 of 95! But glad it's high from what I understand that is good! I would assume your FEV1/FVC is reduced then?

And yes I feel very young to have this but they say I caught it early. Not sure how much that will help. The doctor seems to think I won't progress since giving up the cigs. Though in my research I've not found very many that don't progress.

Thank you again for the comment. I'm glad to learn all I can from others. Hope you are keeping well too!

Hi Suzipete,

according to my understanding your nurse is correct: Your FEV1 and FVC values in the normal range are not suggestive of a ventilatory lung mis-function, and the 6% and 12% variation measured after 12 months may well be within the measurement error of the test and mean nothing. Therefore, they are not considered any further. The fact that your ratio is slightly reduced (depending on which definitions you go by) is suggestive of COPD as your dr has said 12 months ago. But the good news is: it has stayed stable over 12 months. So keep doing what you are doing and hopefully you will stay stable for a very very long time. Do you have any COPD symptoms? Best wishesxxx

Thank you Jen S!

The only synptoms I have are breathlessness when climbing stairs, a restrictive feeling mid-chest and a slight wheeze from time to time. Thabk you so much for your reply and info.

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...,Personally I have NEVER bothered about ANY of these figures etc , its all technical, and up to a point only a matter of opinion , but at the end of the day I'me really only concerned HOW I FEEL , as there is a risk that we Patients start to "Fit in " with how we see and interpret these figures , IE = Someone told my neighbour recently she should'nt walk to the local Post office , because " YOUR EIGHTY TWO, AND AT YOUR AGE YOU SHOULD TAKE THE BUS ". My neighbour replied = " WHATS THE NUMBER "EIGHTY TWO " GOT TO DO WITH IT ? - IT IS ONLY A NUMBER, ITS HOW I FEEL AT THE TIME THATS MORE IMPORTANT AND ITS ONLY THAT WHICH DECIDES HOW I ACTUALLY GET THERE "

Get my meaning folks ! ....... YOUR BODY TELLS YOU ALL YOU NEED TO KNOW - GOOD LUCK !...


That is an excellent way to look at this. And I happen to agree. Ive been obsessing over this diseases since being diagnosed. I think about it all day long. It's not so much the disease that's hindered my life but the constant obsessing about what's going to happen. I hope to be more like yourself and concentrate on how I feel instead of obssessing over what some numbers say. Thank you for this reminder and response.

Fev1 (Forced Expiry Volume) is the volume of air that you can blow out in 1 second.

FVC (Forced vital capacity) is the TOTAL volume of air that can forcibly be blown out after full inspiration... 12 seconds blow usually allowed.

Normal = should be able to blow 80% of your total capacity in 1 second.

Fev 1 is measured in litres ( so 2 or 3 or thereabout). If big number 25, 40, 60 80 etc that is % of predicted.

Predicted numbers is an average of normals that include big people with small lungs and small people with big lungs. So taken by itself Fev1 could look 'obstucted' because your blow is less than average... but you could have small lungs thus actually be normal!

Whilst someone else could blow 90% predicted but have big lungs and actually be obstructed.

So they need to take into account the size of your own lungs hence the ratio of blow(FEV1) to volume (FVC) where FEV/FVC 75%, arguably, is bottom of the normal range, or top of the obstructed.. depending on your history (smokers likely to be deemed obstructed).

There is another measure that tells where the obstruction occurs. I fail on the last quarter of the FVC blow which indicates small airway obstruction. See link

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Thank you so much for this information! You explained it so clearly! I have never considered the thought of lung size before. Thank you again for taking to time to reply.

Things can get confusing with FEV1/FVC because that division produces n% which is your personal %, then that is compared to norms which is also stated as a %. So yours could be 68%, which is 90% of predicted.

So you/we need to know which figure you're talking about.

I ask & get a copy of the printout from the tester (nurse or consultant).

Yes! Thank you!

I have a full copy they are getting ready for me. Thank you for your reply.

Thank you for that explanation. I must admit I get very confused on the numbers thing and find it hard to grasp. I just concentrate on my FEV1 which I do understand :) x

hi suzipete, sorry to hear you have this horrid condition, it is hard to get around all the figures, and everybody is different and usually have other conditions which can further cloud other things. my lung finction had dropped from 67% to 34%, in the space of 10 months, i collapsed and it turned out to be a substantial bi-lateral pulmonary embolism,and ended up in hospital for 10 days and one another visit of 2 days, not that you should have anything as bad, but it took me 6 months of hassling and pushing and in the end begging for someone to take notice. So what I am saying is dont take it all on face value and if you feel something is wrong then you have to keep pushing your doctors. i had a dvt in my leg whilst all these things were going on and he just prodded it and said “oh thats just inflamed viens” got it completely wrong and was very dismissive, so demand answers!

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Thank you so much! I absolutely agree. We have to be the ones responsible for our own health! I'm so sorry you have had a difficult time of it. Thank goodness you pushed for more answers!

When I said your FEV1/FVC ratio was in the normal range I was assuming you were at least 50 years old, like most with COPD. A ratio of .73 at age 37 does indeed suggest COPD.

Btw, a rough calculation suggests that your FEV1 and FVC has not declined by

6 and 12 PERCENT, but by 6 and 12 MILLILITRES . . .

Thank you for this clarification!! Is the milliners loss something to be concerned about? I guess I'm confused why the doctor states I have not progressed when I've had this decrease? Thank you so much again for you help.


Both FEV1 and FVC gradually decrease as part of normal aging.

Highly variable but averages about 30 ml per year in healthy non-smokers:

I can not thank you enough for all of the information!

You're doing a pretty good job of it.... :)

PS a Milliners loss is if your hat blows off... LOL!!!

Ha!! :)!! Thank you Soulsaver!! That makes me feel better!

I have just been diagnosed with copd fev1 at 65% at the age of 33. I've never been a heavy smoker ranging from a few weeks no cigs to a few weeks between 5/10 on off or the past 5 years. They saying it's because I've had chronic asthma since being very young....has anybody else had this and I'm just wondering the progression rate in general. Thankyou

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