14 year old boy fainting

[Cats49]

My DS fainted this morning. He had just got up from lying down position on bed (had already been up for a while and was dressed, had breakfast),walked out onto the landing and then I heard a thud. I rushed out of the bathroom and he was lying on the floor with eyes open looking dazed. He wasn't fitting or anything. Just said he had felt dizzy when he walked out of his room but couldn't remember falling down. I got him to lie down again and within a couple of minutes he said he felt fine again and continued getting ready for school. He has been fine all day. Is this common in teenagers? (He is going . I just wondered if I should get appt with GP to check iron levels or something.
Any advice much appreciated!

Is he tall and thin, recent growth spurts? This body type and teenagers can be prone to fainting. Had he only just got out of bed? Postural hypotension is possible, basically low BP caused by going from a lying position to standing dropping the blood pressure and making you dizzy. Neverthless it wouldnt hurt to get him checked for anaemia blood pressure etc as teenagers can have shocking diets despite our best efforts.

Yes he is tall and very skinny - runs in our family as my brother is ultra thin and 6ft 3 inches tall. I do try to give him a good diet (eats fruit and veg daily) but he does squeeze in extra junkie food as often as he can. He hadn't been IN bed, just lying down on the bed and then he got up to get organised for school.
Thanks - I will drag him to the GP if I can to check for anaemia

Just realised there was an error in my first post. 7th line should read 'He is going through puperty and a growth spurt at the moment' Don't know why tha line got deleted.

He's probably fine and healthy just a combination of tall/skinny/growth spurt and lying down! Did you think I was psychic - I wish [hmmm] lottery and all that!
Always a good idea to get checked out though

Thanks guys!