Macfadyen, who is still only 28-years-old, now has his sights set on returning to University where he will study Sports Science focussing on strength and conditioning.
During his studies at Napier University, Donnie will work with Edinburgh Rugby Club to put his experience into practice.
Despite enduring a run of serious injuries, Macfadyen was able to continue his playing career but has decided to leave with a view to getting the most out of his off-the-field role.
Donnie, who has won 11 caps for Scotland, said: "I take with me some fantastic memories of playing for Glasgow. Injuries have played such a big part in my career, but all the good times by far outweigh the bad."
Having played such a big part in the development of future back-row talent, such as John Barclay, Madcfadyen is pleased to see the Warriors go from strength-to-strength in his department. "It's great to see such talented young guys come through. Glasgow have really set themselves up for a good run next year and I look forward to seeing both Scottish professional teams flourishing in the years ahead."
Macfadyen made his Scotland A debut in the 33-13 victory against Italy A at Old Anniesland in March 2001 before getting his first Scotland cap as a second-half substitute against Canada on the 2002 North American tour during which he played in all six matches. He travelled on the tour straight from duty with the Scotland 7s squad in the IRB Sevens World Series competitions at Twickenham and Cardiff.
A string of injuries meant he had to wait another two years for his next representative action but started in all three Tests on the 2004 summer tour of Australia and also appeared in the first game of the tour against Queensland.
He retained his starting berth at openside flanker for the 2004 Abbey Autumn Tests opener against Australia at Murrayfield, the next match, scoring a try, in the historic 100 - 8 victory over Japan and the following Test, again against Australia.
Macfadyen scored his second try for Scotland after being introduced to the second Test against South Africa in Port Elizabeth in the summer of 2006. The previous week he returned to international action against South Africa in Durban after more than 18 months out of the Scotland team through a knee injury.
He has now played four times for Scotland A, three as a replacement and starting in his most recent appearance, the victory against Italy A at McDiarmid Park in February 2007.
He captained Scotland under-21 throughout the Southern Hemisphere Alliance tournament in the summer of 2000, including the draw against Australia and the victory against Tonga.
In season 2000/01 he captained Scottish Students against both their French and Welsh counterparts. He was the Lloyds TSB Young Player of the Year in season 1999/2000 during which he played eight times for Scotland under-21, seven as captain.
He played for Scottish Schools in 1996-97 (while he was at Edinburgh Academy) and after a sojourn with London Scottish he joined Glasgow - then called Glasgow Caledonians - for the 1999/2000 season.
He also played in the December 1999 victory over the New Zealand Youth XV at Riverside Park, Jedburgh. He marked his debut Scotland appearance (uncapped) against the Barbarians at Murrayfield in 2001 with a try.
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