Cycling and low sugar level

umer76

Hi i have started cycling and i am not regular with it. I usually do once a week but whenever I do it for half an hour and in the last 5 minutes and when i finish my sugar level starts going down feel bit dizzy and heartbeat goes very fast. This condition lasta for next half an hour and then i drink something sweet and starts getting better. What am i doing wrong? Is half an hour too much for me? Should i drink before going on cycling? This situation discourages me to go for cycling on regular basis. Your suggestions will be appreciated.