Hello. I'm Dr. Christensen.
I'm sorry you've been having problems. Unfortunately, it won't be possible to diagnose your condition or offer any treatment advice without a thorough evaluation. However, I can offer some information about the possible causes of recurrent fainting; you'll need to see your doctor again to explore some of these issues.
Anemia is a fairly common cause of lightheadedness and fainting. I presume your blood tests included a complete blood count
(CBC) which would have ruled out anemia. Iron deficiency
is only one cause of anemia, so just having your iron level checked isn't sufficient to rule out anemia.
People who have intermittent dysrhythmias (abnormal heartbeats that only occur occasionally) can pass out without much warning, although cold sweats, blurred vision and nausea can precede a fainting episode. Many people with dysrhythmias can tell when their pulse is irregular, but not all do. If your heart is beating normally when you see your doctor, this is a problem that can easily be missed.
Hypoglycemia, or low blood sugar, is an unusual cause of fainting. Because your blood sugar can be normal between hypoglycemic episodes, this is another problem that may not be detected with routine blood tests.
Many people who faint repeatedly are suffering from instability of their autonomic nervous systems. (This is the part of your nervous system that controls your heart rate and blood pressure.) There are several forms of autonomic instability, including vasovagal instability and postural orthostatic tachycardia syndrome
Seizures can cause fainting, too. Your history of childhood epilepsy
may or may not have a bearing on your current problem, but this certainly deserves further investigation. (Not all seizures cause the classic "grand mal" convulsion; many are more subtle.)
Metabolic and endocrine disorders, such as hypothyroidism, diabetes or Addison's disease, can be associated with fainting. Some of these problems could be picked up on routine blood tests, but others require special testing.
Dehydration is a very common, but often overlooked, cause of fainting. People who don't drink enough water and who work in warm environments may pass out simply because there's not enough fluid in their circulatory system.
If your fainting spells persist, your doctor may want to order ambulatory cardiac monitoring (this requires wearing a small heart monitor for a few days), more blood tests, and possibly a consultation with a neurologist
I hope that all helps, and good luck! (By the way, your vitamin D deficiency is unlikely to be the cause of your fainting spells, but this issue should be addressed as it can contribute to other long-term problems, such as osteoporosis.)