My iron serum is 26 ug/dl expected range is 36-145 is that really dangerous?

No, but should treat: This is not unusual in women who are menstruating as you are losing iron with every menstrual period. It is of more concern if you are anemic, but even if you are not it is wise to eat more iron-rich foods and/or take an iron supplement. The best tolerated supplement is iron bis-glycinate- see https://theheartysoul.com/iron-absorption/ For food sources see https://tinyurl.com/yd6jv5lg

Serum iron: Your serum iron indicates that you are anemic and can benefit from oral iron

You decide: Your body uses iron (the element) as a cofactor in many metabolic systems that fuel your energy. It is also one of the most important elements your body needs to create the blood cells you need to survive. Your low level suggests low intake or increased loss of your body iron. You can replenish it rather easily unless you have a medical condition causing excessive loss. Discuss this with your doc.