PRECREST is a two phase protocol for Huntington's disease in which 60 premanifest and at-risk subjects will first be randomized into a double blind placebo controlled dose titration study bringing them to 30 grams daily or their highest tolerated dose. This phase will establish the highest tolerable doses in premanifest HD and permit the detection of toxicity and intolerability with attribution to active compound versus placebo, and enable a dose response assessment of biomarkers. In the second phase, all subjects will enter a year long open-label treatment on 30 grams daily (or their highest dose) of creatine to assess long term exposure to high dose creatine and its long term impact on various biomarkers.