The hyponatremia is caused by a relatively smaller loss in total body water. 1  any cause of hypovolemia such as prolonged vomiting, decreased oral intake, severe diarrhea. 2  diuretic use (due to the diuretic causing a volume depleted state and thence ADH release, and not a direct result of diuretic-induced urine sodium loss)
Biotin is safe but is not likely to do much to help your hair grow unless you are deficient in biotin, which is uncommon. A reasonable dose is 5 mg. However, you may get better results by taking a quality multivitamin, eating a healthy diet rich in organic fruits and vegetables, avoid junk food and getting adequate sleep.
Depending on your case, your doctor might recommend a higher dose. For diabetes, for example, one study used 2 milligrams in combination with 600 micrograms of chromium. Even at high levels, biotin appears to be fairly safe. Researchers don't know at what dosage biotin might start to pose health risks.