Will I lose my messages if I upgrade my iPhone?

I have the iPhone 5 now and will be upgrading to the iPhone 5S and I have messages from a person that are quite sentimental and I'm not ready to get rid of them. If I upgrade will I lose them? Is there a certain way to upgrade my phone without losing it? Not sure if all of it transfers? Thanks.

Added (1). Do the messages back up on iTunes?

Lol should have got an android phone. The 5s is the same *** over and over

You could screenshot them and send them to your new device (how to screen shot- press home button and power button @ the same time to take a picture of your display) or you could send the screen shots to someone and they could save them for you then they could send them back to you on your new device. Hope I helped!

If you're worried manually back up your current phone to itunes and then restore from that backup to the new phone.

Foreword them to your email.