I've used as much data in one day as I normally use in a month. I was perplexed by this at first, but then I noticed that each speedtest I was doing was using about 10 MB of data. I've done about 30 LTE speedtests in the past 24 hours which equates to about 300 MB of data consumption. Apparently, it has to download a large file in order to run the download and upload tests.
Warning - LTE speedtests use a lot of data | iPhone and iPad Forums at everythingiCafe
Sooo Lte came to my city around midnight on the 1st... coincidental that was when my monthly plan starts over. So I was running speed test showing like 57Mb/s I ran it about 6 times out of excitement ... huge mistake it used a little over 100MB of my data plan between showing DL and UL speeds smh. You don't notice the small amount of data its consuming when its only running 3.4Mb/s for 5 seconds each time but 57 is a huge diff. Just be forewarned lol. That's valuable data I could have saved. So I won't be doing much speed test bragging to my friends lol.
[Warning] Speed Test Eats Data - xda-developers