Iron panel was normal other than my ferritin. It was only 20, which is low. My iron level was normal with CMP & CBC. WHAT causes just a low ferritin?

Can be okay . 24 nano grams is often given as the bottom of the reference range, so 20 is not a serious sign of illness. The ranges are set so that some healthy folks fall outside. Vegetarians and blood donors often run low. Keep an eye on it.

Related Questions

High iron serum-167, low ferritin-113.Cbc&cmp normal. Symptoms:fatigue and mild anxiety. Are symptoms of iron overload possible with low iron 'storage'?

No. It does not appear that you have abnormal iron stores. Your fatigue and anxiety may be related. Please ask your doctor if you may be depressed as that can explain both and depression is treatable. Read more...
Iron. Not sure what your reference values for labs are but the ferritin does not look low. See if you can get an iron percent saturation that will be useful. If it is above 55%, you should look for iron storage diseases like hemochromatosis. Read more...