is it true that a iron level 9 will not result in any symptoms (said doctor)

I had bloodwork done 4 months ago in september when I was having an awful month long flare up/stomach virus of some sort. The bloodwork revealed that I had very low iron, at a 9, and also low B12. I have been supplementing a low dose of iron (blood builder); as I have IBS, and just went through that awful stomach flare, so I was worried about upsetting my stomach with the iron. 5 months later my iron is still at a 9. My B12 has entered into normal range with supplements. My dr is having me try feramax iron supplements. He said that at my iron level I should not be feeling any side effects because I’m young. Is this true? I suspect i’ve had low ish iron for a long time as i’ve always gotten dizzy and staticy vision when I stand up, often feel like i am going to pass out in the shower, get ringing in my ears when i stand up (the same feeling i get when i pass out from bloodwork), and racing heart rate etc. In the past 4 months I’ve been very tired, have had no energy, and have even had to take breaks when going on a walk as I have no energy (I am an otherwise healthy 20 year old, beside my stomach issues). Is it possible that my low iron has caused these symptoms or is it true that i shouldn’t be experiencing symptoms? All of my other levels like hemoglobin and blood related were normal.