What Causes Dizzy Spells Along With Rapid Heart Rate?

Today I felt dizzy, my heart Was pounding and my hearing was muffled. I fell to the floor and couldn t get up. My vision gave out and all I saw was white. I managed to open the fridge and drunk some juice, most of it spilled on my shirt as I couldn t balance or hold it Properly. After 20 min I was able to stand up and start to refocuse. I wasn t hungry, I had just finished a protein shake for breakfast. only 3g carbs. I ve never had this happen before and after 8 hrs I still feel strange. What could this be?