Nettles is nutritive and detoxifying for the blood on many levels. Generally, the time herbs take to work is about one month for every year we have experienced the concern. But there are so many factors. Have you read my article called “Quality is Everything!”? You may find it at:
http://www.wisdomofhealing.com/articles/quality-is-everything/

The other most important factor is your condition, and your body’s ability to self-repair. After years of slowly breaking down, the body may respond quickly to a gentle, yet powerful herb like nettles; or it may take a long while.

Also, is your nettles tincture organically grown? Are you taking it at least four times daily (and at least 30 minutes apart)?

Your body is wise to let you know that regular iron supplements don’t work for you. The iron used to make nearly all of the iron supplements on the market, whether so called ‘natural’ or not, should only be used to make frying pans, etc. It is NOT utilized in the human body, and may indeed be a bit toxic, causing constipation and irritability.

I wonder, have you tried the liquid herbal iron called Floradix? It is superb, helps with energy and vitality levels, and is completely non-constipating (and non-irritability provoking!) You can find it at almost any real health food store or herbal pharmacy.