Why do I have dizziness and fainting?

My friend is a male and years old hes had a problem for 3 years but has got worse in the last 3 months. When he stands up of sits down or is walking for a long amount of time he feels dizzy and hes 'eyes go black' - this only lasts for around 6 seconds...

Actually my dad has his headache, and I wanted to find a way to cure it... He has his head ache frontal part of the head, he said that it was a dizziness or fainting feeling whenever he start to lay down and when he turn his head it constantly follows...

I am a 38-year-old female who has sudden onset of heart palpitations, dizziness, near fainting, and leg weakness several times a month. It comes on after I have been sitting and begin walking. I walk a few feet before it starts. I have to hold onto something...

Dizziness, fainting, shortness of breath, occasional headaches. I can't run. I physically can't because it's too hard to breathe. I'm about 155cm tall and weigh ...show more

Yes I am having these right now, a burning chest pain, I feel very tired like I ran for hours with no stopping, and I am almost fainting even If I am sitting on a chair in front of a computer. And doesn't matter how much I breath, I feel very tired....

I tend to get dizzy a lot and I've fainted like 4 times in my life. I am a young teen and I have been trying to drink lots of water but it doesn't seem to work. What can prevent my dizziness for school tomorrow or just anything really.

NOTE: do not answer if you do not have medical training/ know how!! I am a 22-year-old female in good health except for the following issue and severe acid reflux. I am thin and tall.  I passed out on Monday after experiencing the same symptoms...

This happens for some cycles on a yearly basis...