I Have Spells With The Following Symptoms: I Get Really

I have spells with the following symptoms: I get really hot, shaky, then weak and fall down. Occasionally complete faint. The symptoms are exactly the same every time. Only salt helps stop this problem if I eat it as soon as I feel an onset coming on. Have been tested for diabetis more than once and everything is fine there, sugar makes symptoms worse. Any ideas what this could be?