The Lausanne-based Court of Arbitration for Sport endorsed last year's decision by the national federation to ban her till September 6, meaning she will miss the London Olympics, which run from July 27 to August 12.
Balciunaite, who turns 33 on Tuesday, will be stripped of the European title she won in Barcelona in 2010 and have to return the medal, the federation added on its website.
The Lithuanian, who won the gold in two hours, 31 minutes and 14 seconds, tested positive for traces of banned synthetic steroids. She has denied taking banned substances.
Russia's Nailya Yulamanova, who won silver in Barcelona is likely to be upgraded to gold.