9 is very low! I feel like death if mine are under 30 and symptomatic under 50. And ferritin levels are very difficult to raise. Mine's taken about 3 years because I struggle to tolerate iron supplements.
Treatment for low ferritin really seems to vary wildly. Mine was 8 when first tested and my GP said just eat more iron rich foods! I explained that I already ate a lot of iron rich foods she said nothing.
I did my own research and put myself on supplements and have tried various things over the years.
Some people I've spoken to were put on supplements by the GP and some were given iron infusions. So really mixed.
Liquid iron contains very little iron do unlikely to raise your levels by much.
The starting point is 210mg ferrous fumerate 3x a day taken with 500mg of vit c each time to aid absorption and reduce constipation.
If you can't tolerate ferrous fumerate then try ferrous bisglycinate (gentle iron) same amount again with vitamin c.
Some people can raise ferritin by eating 200g liver per week.
Others by eating lots of dark green leaves with each meal.
Make sure you don't have tea or coffee within a hour or two of your main iron rich meal as reduce absorption. As does calcium.
I've tried loads of things. Some success with eating tons of watercress but I can't stomach eating that amount after a few months so stopped then.
Have since then been on 4 x active iron tablets a day with vitamin c and just in the last few months got my ferritin over 50. Yay!
Do you know why your ferritin is so low? Do you have heavy periods?
Mine was caused by hypothyroidism causing heavy periods which then caused low ferritin (plus hypothyroidism reduces stomach acid so makes absorption of vitamins harder).