When you have an electrolyte deficiency some symptoms that you'll experience are constipation and/or diarrhea, Vomiting, Nausea, seizures and convulsions, fast heart rate, lethargy, fatigue and an irregular heart beat.
You can also experience cramping and even hemorrhoids.
You can replace lost electrolytes by drinking some Gatorade or even Pedialyte.
In some cases if your lost electrolytes are more severe then you may need to go to the hospital and have an IV put in.