The most common cause of such spells in a female is a low red blood cell count, measured by what is known as the hematocrit. Females lose more blood then men and often suffer from what is called iron deficiency anemia. Our red blood cells are constantly replenished and we lose about 1/54th of them every day. A single aspirin can cause loss of a teaspoon of blood. Bleeding from hemoroids can also cause a low hematocrit.
Usually there is a co-factor (i.e. low blood pressure), dehydration, and sometimes an overly sensitive vagus nerve. The vagal system controls the heartbeat. Jackie Kennedy used to suffer from such spells.
It is unlikely you have something growing in your head, but an MRI is probably indicated. They provide free MRI's from a truck in many cities.
The drill is as follows:
(1) Learn what your hematocrit is.
(2) Monitor your blood pressure. Stay hydrated. Drink electrolytes every day such as Gatorade. If your blood pressure is low, ask your physician why this is the case.
(3) If your blood pressure is low, don't hesitate to use moderate amounts of salt.
(4) You require an occult stool test. This is done at home and usually mailed in. It determines if you are losing blood in the intestinal tract.
If you feel a fainting spell coming on, immediately lie down, and if possible put a pillow under your feet to raise them 4-12 inches.
I would purchase a blood pressure meter and a pulse oximeter. Keep a record of the readings.
I also have fainting spells. They happen once every 6-18 months, and have for the last 10 years...I'm 27. When this first started happening, I had every test imaginable and they found nothing. It's frustrating, but even more than that, it's scary. Last week I fainted from a standing position and smacked my face on the floor, resulting in a busted lip and a headache that hasn't gone away in the last 8 days - likely a concussion. Anyway, I commiserate and wish I could offer advice, but I don't really know anything either. I am a healthy, active, 27-year-old man. Sometimes (usually) I feel the fainting coming on, but two or three times (including last week) I have awoken in the middle of the night feeling sick, then I faint in - or on the way to - the bathroom. I'm pretty worried but feel like there's nothing I can do!
JT
I also have faintings out of no where. I first feel very light headed, then right when i'm about to say something or sit down i just blackout. Sometimes it looks like i am having a seizure. It is very scary to watch, im told. Then i just wake up like nothing happend, a little weak but thats it. Upon wakening my vitals all are normal. I have lots and lots of doctors, all of them are unknowing to my condition because all the hundreds of tests iv undergone have come back normal. It's very odd!!!!
Since it's not a heart problem, I think that it could be iron def. or even vitamin deficiency. It could be stress, dehydration as the people in here told you. I don't know if you have a family history or not, but perhaps it could be a possible thyroid problem. I am hypothyrodic and the first symptoms I had was light headedness ans weakness. Take a simple general blood test to see the levels of your blood cells and your TSH (thyroid hormone).
Its possible you have low blood sugar or are a little dehydrated. Have you tried eating anything when you feel these spells coming on? Are you drinking 6-8 glasses of water a day?
I had a few weeks where I got dizzy (due to a chiropractor). I ended up in emergency cause I knew I was going to faint again. They did blood tests on me.... they thought the machine was broken until another lady had blood tests and hers came back fine. I had very little potassium - so low they thought the machine was broken. I was put on potassium pills for a few days and was back to normal again. I had been eating properly and exercising - so there was really no reason as to why I had a potassium deficiency. You could try taking women's one-a-day or some other daily vitamin, to see if it helps.
I have a friend that had the same type of episodes and her doctor told her she was iron deficent because her periods were heavy. Have your doctor do a simple blood test to check.