Can anything be done (medication or lifestyle change) to raise blood pressure?

Usually: Low blood pressure is generally desirable, but if there is lightheadedness with position change or other symptoms of low blood pressure, need to ensure no underlying problems- low thyroid, or low cortisol, or slow heart rate. Need to ensure good hydration status, consider liberalizing salt intake. Compression stockings can be quite helpful. Some medications may include midodrine or florinef (fludrocortisone).

Yes: Occasionally, i advise people with low blood pressure to consume salty foods, because the higher sodium content can bring up the pressure. Should drink 2 liters/day. In rare instances, I use Fludrocortisone to increase bp. In really tough cases, I use midodrine. These are both prescription meds. I have seen people use theophylline for this, and i suppose you could try good old fashioned coffee too.

What is the cause: This will direct treatment which can vary widely from hydration to increased sodium to Florinef (fludrocortisone) to midodrine, etc.