Low sodium levels, also known as hyponatremia, can be caused by several conditions and factors, including:

• Certain medications such as diuretics (water pills), antidepressants, and pain medications that affect the balance of sodium and water in the body.
• Medical conditions like heart failure, kidney disease, liver disease, and adrenal gland disorders (e.g., Addison's disease) which cause fluid retention or sodium loss.
• Syndrome of inappropriate antidiuretic hormone secretion (SIADH), where the body retains too much water relative to sodium.
• Excessive water intake, especially during endurance activities, which dilutes the sodium concentration in the blood.
• Severe vomiting, diarrhea, or sweating that causes loss of sodium and electrolytes.
• Hormonal imbalances such as hypothyroidism or adrenal insufficiency.
• Recreational drugs like ecstasy (MDMA) that increase the risk of hyponatremia.

Overall, low sodium usually results either from sodium loss from the body or from excess water diluting sodium levels in the blood.