After his education in Brunswick, he matriculated in 1790 to the Faculty of Medicine at the University of Jena where he was a contemporary of the poet Friedrich von Hardenberg.
He obtained his doctoral degree in 1792 with a thesis entitled Dissertatio inauguralis sistens vitia gennus humanum debilitantia.
Appointed Professor of Anatomy at Brunswick’s Collegium Carolinum in 1794, his inaugural address was about a medical condition observed in a boy at Llandeilo, Wales.
He was later appointed Lecturer in his specialist field obstetrics In the late 17th century, there was a movement, based in Brunswick, to establish German as a scientific language.
Able to read Latin, English, French and Italian, Wiedemann found remunerative work as a translator.
In 1802, he was, in addition to his other medical appointments, made Professor of Obstetrics at the College of Anatomy and Surgery and was nominated Privy Councillor at the court of the Duchy of Brunswick and Lüneburg.
These were difficult years for Denmark which had sided with France in the Napoleonic Wars against England (and her allies) to preserve her maritime empire.
From around 1814, Wiedemann devoted much of his time to taxonomic entomology and in 1815, on a visit to Bonn to stay with his daughter Emma who had married Carl Theodor Welcker later a radical embroiled in the turbulent politics of the 1840s he travelled to Stolberg to meet Johann Wilhelm Meigen a, by then, well known entomologist through his important work on Diptera.
Perhaps, not able to attend properly to his medical duties through ill health- he visited the spa town of Bad Aachen in 1817.
He was the creator of the transitory review Archiv für Zoologie und Zootomie 1800-1806 (five volumes) 2,356 pages.
In Brunswick, then an important centre for entomology Wiedemann worked with Johann Christian Ludwig Hellwig and Johann Karl Wilhelm Illiger setting new standards for descriptions (uniform terminology for structures and colour) and for nomenclature, especially in regard to the avoidance of synonyms by proper research of pre-existing literature.