Some words from Dr. Jay Wortman a lowcarb expert and type two diabetic on lowcarb and salt.

“When you cut the carbs your kidneys will release sodium. This is why people lose some water initially and why blood pressure also tends to get better on low-carb. If you are not careful to replace the lost sodium sufficiently by adding salt to your food, you will experience the effects of mild hypo-natremia. These are: headache, constipation, weakness, fatigue, low-blood pressure, othostatic hypotension and possibly leg cramps. If you get a blood test you may find that your potassium is low, too. Unfortunately, there is no reliable blood test for magnesium but it may also be low. Supplementing with salt should correct these problems. You don't need to take a potassium supplement, it will correct if you eat enough salt. Some people will have a persistent magnesium deficiency that will require supplements. This would be manifested by leg cramps and hyper-reflexia (something your doctor can check). To correct this you should take a slow-release Mg++ supplement daily. 

Many people make the mistake of restricting salt and drinking lots of water when on a low carb diet. This is virtually guaranteed to cause problems. When you look carefully at the studies that report equivocal results with a low-carb diet, this is invariably one of the reasons.”