Yes, VPN use extra internet due to it's structure. But you can do the following things to minimize it's effect.

Experiment with servers that are geographically close to you to ensure low latency (delay). To understand more about latency se the link above.
If you are connecting with L2TP/IPSec, try using OpenVPN and vice versa. If you are using OpenVPN, try connecting to the TCP service. See L2TP vs OpenVPN.
Wait a few hours and check it again. There may be an outage somewhere on the Internet that is causing congestion as data is re-routed over backup links.
Was your VPN speed faster before? If you've changed your firewall or antivirus software or installed any other software since you last connected, you may want to try disabling the software temporarily.
Are you in a different location that the last time you connected? You should expect vastly different speeds depending on where you are connecting from.
Are you on wifi? If you are connecting from behind a wifi router/access point you may have insufficient bandwidth to utilize your full raw connection speed. Every user connecting to the wifi router shares the routers bandwidth. You can try changing the wifi channel that you are connecting on (see your wifi router manual for more information).
Are you on a mobile/tablet/netbook with limited processing power? Encryption requires significant processing power and trying to stream high definition movies over the VPN may cause the device to reach its limitations.
Try rebooting the device you are connecting from. Rebooting can help by applying configurations that are not saved and reloading the latest drivers/applications back into freshly cleared RAM. It's always worth trying if all else fails.

www.downloadvpn.org