The Glasgow prop collided with Wyn Jones' head when clearing out a ruck in Scotland's 25-24 defeat in Edinburgh on Saturday.
Fagerson's four-week suspension means he will miss Scotland's remaining Six Nations matches against France, Ireland and Italy.
Fagerson told a Six Nations disciplinary hearing he accepted the act of foul play, but did not believe the offence warranted a red card.
"The disciplinary committee found that the act of foul play warranted a mid-range entry point, six weeks' suspension, and reduced that by two weeks to take account of mitigating factors, including his admission of foul play, good disciplinary record and remorse," read a Six Nations statement.
"Mr Fagerson is therefore suspended for four weeks and, given his playing schedule, he will miss the three Scotland matches in the Guinness Six Nations Championship against France, Ireland and Italy, and one further match to be determined."