Arkansas inmate Tom Henderson appeals the district court’s 1 dismissal of his 42 U.S.C. § 1983 action. Following de novo review, see Moore v. Sims, 200 F.3d 1170, 1171 (8th Cir. 2000) (per curiam), we affirm, see 8th Cir. R. 47B. We agree with the District Court that Henderson did not state a claim, as he did not show defendants were deliberately indifferent to his serious medical needs, see Estelle v. Gamble, 429 U.S. 97, 104, 97 S.Ct. 285, 50 L.Ed.2d 251 (1976), or to conditions posing an “unreasonable risk of serious damage to his future health,” see Helling v. McKinney, 509 U.S. 25, 35, 113 S.Ct. 2475, 125 L.Ed.2d 22 (1993). We also conclude that the magistrate did not err in denying Henderson leave to amend to add claims challenging his conviction, as he requested a sentence reduction and thus the claims would be barred by Preiser v. Rodriguez, 411 U.S. 475, 489-90, 93 S.Ct. 1827, 36 L.Ed.2d 439 (1973) (habeas corpus is exclusive remedy for prisoner challenging fact or length of confinement). See In re NVE Corp. Sec. Litig., 527 F.3d 749, 752 (8th Cir. 2008) (de novo review of denial of motion to amend complaint based on futility). Finally, we conclude that the district court did not abuse its discretion in denying appointed counsel. See Phillips v. Jasper Cnty. Jail, 437 F.3d 791, 794 (8th Cir. 2006) (standard of review). We also deny as moot Henderson’s appellate motion for appointed counsel.