diff --git a/examples/make_realtime/main.rs b/examples/make_realtime/main.rs
index 104b826..ab491ba 100644
--- a/examples/make_realtime/main.rs
+++ b/examples/make_realtime/main.rs
@@ -1,8 +1,7 @@
 use nix::unistd::gettid;
 use std::thread;
 
-// use rtkit_client_rs::::RTKitProxyBlocking;
-use rtkit_client_rs::{make_current_thread_realtime, Error};
+use rtkit_client_rs::{set_current_thread_priority, Error};
 
 fn main() {
     println!("Main tid: {}", gettid());
@@ -11,10 +10,21 @@ fn main() {
 
 fn important_thread() {
     println!("Important thread tid: {}", gettid());
+
     let requested_priority = 40;
-    let actual_priority = make_current_thread_realtime(Some(requested_priority));
+    let actual_priority = set_current_thread_priority(Some(requested_priority.try_into().unwrap()));
     match actual_priority {
-        Ok(actual_priority) => println!("Requested priority: {requested_priority}, Actual priority: {actual_priority}"),
+        Ok(actual_priority) => println!("Requested priority: {requested_priority}, Actual priority: {}", actual_priority.value()),
+        Err(Error::PermissionDenied) => println!("Permission denied. Do you have polkit rules set up, or otherwise have the necessary permissions?"),
+        Err(e) => println!("Internal zbus error: {e}"),
+    }
+
+    let requested_nice_level = -10;
+    let actual_nice_level = rtkit_client_rs::set_current_thread_nice_level(Some(
+        requested_nice_level.try_into().unwrap(),
+    ));
+    match actual_nice_level {
+        Ok(actual_nice_level) => println!("Requested nice level: {requested_nice_level}, Actual nice level: {}", actual_nice_level.value()),
         Err(Error::PermissionDenied) => println!("Permission denied. Do you have polkit rules set up, or otherwise have the necessary permissions?"),
         Err(e) => println!("Internal zbus error: {e}"),
     }
diff --git a/src/lib.rs b/src/lib.rs
index 99c4a74..89afd17 100644
--- a/src/lib.rs
+++ b/src/lib.rs
@@ -1,10 +1,25 @@
 mod low_level_zbus_api;
+mod types;
+
+pub use types::{NiceLevel, Priority};
 
 #[derive(thiserror::Error, Debug)]
 pub enum Error {
     #[error("Permission denied")]
     PermissionDenied,
 
+    #[error("Invalid PID")]
+    InvalidPid,
+
+    #[error("Invalid thread ID")]
+    InvalidThreadId,
+
+    #[error("Got invalid max priority from RTKit")]
+    InvalidMaxPriority(i32),
+
+    #[error("Got invalid min nice level from RTKit")]
+    InvalidMinNiceLevel(i32),
+
     #[error(transparent)]
     ZbusError(#[from] zbus::Error),
 
@@ -13,9 +28,9 @@ pub enum Error {
 }
 
 /// Helper for [make_thread_realtime], uses the current thread's tid.
-pub fn make_current_thread_realtime(priority: Option<u32>) -> Result<u32, Error> {
+pub fn set_current_thread_priority(priority: Option<Priority>) -> Result<Priority, Error> {
     let thread_id = nix::unistd::gettid().as_raw().try_into().unwrap();
-    make_thread_realtime(thread_id, priority)
+    set_thread_priority(thread_id, priority)
 }
 
 /// Elevates the realtime priority of a thread as close as possible to the requested priority.
@@ -23,26 +38,20 @@ pub fn make_current_thread_realtime(priority: Option<u32>) -> Result<u32, Error>
 /// If no priority is specified, the maximum priority allowed by the system will be used.
 ///
 /// Returns the actual priority that was set.
-pub fn make_thread_realtime(tid: u64, priority: Option<u32>) -> Result<u32, Error> {
-    debug_assert!(
-        priority.is_some_and(|p| p <= 99),
-        "priority must be between 0 and 99"
-    );
-
+pub fn set_thread_priority(tid: u64, priority: Option<Priority>) -> Result<Priority, Error> {
     let connection = zbus::blocking::Connection::system()?;
     let proxy = low_level_zbus_api::RTKitProxyBlocking::builder(&connection)
         .cache_properties(zbus::proxy::CacheProperties::No)
         .build()?;
 
-    let max_realtime_priority = proxy.max_realtime_priority()?;
-    debug_assert!(
-        (0..=99).contains(&max_realtime_priority),
-        "max_realtime_priority must be between 0 and 99"
-    );
-    let priority = priority.unwrap_or(max_realtime_priority as u32);
+    let max_priority = proxy.max_realtime_priority()?;
+    let max_priority = max_priority
+        .try_into()
+        .map_err(|_| Error::InvalidMaxPriority(max_priority))?;
+    let priority = priority.unwrap_or_default().min(max_priority);
 
     proxy
-        .make_thread_realtime(tid, priority)
+        .make_thread_realtime(tid, priority.value())
         .map(|_| priority)
         .map_err(|e| match e {
             zbus::fdo::Error::AccessDenied(_) => Error::PermissionDenied,
@@ -55,33 +64,91 @@ pub fn make_thread_realtime(tid: u64, priority: Option<u32>) -> Result<u32, Erro
 /// If no priority is specified, the maximum priority allowed by the system will be used.
 ///
 /// Returns the actual priority that was set.
-pub fn make_process_thread_realtime(
+pub fn set_process_thread_priority(
     pid: u64,
     tid: u64,
-    priority: Option<u32>,
-) -> Result<u32, Error> {
-    debug_assert!(
-        priority.is_some_and(|p| p <= 99),
-        "priority must be between 0 and 99"
-    );
-
+    priority: Option<Priority>,
+) -> Result<Priority, Error> {
     let connection = zbus::blocking::Connection::system()?;
     let proxy = low_level_zbus_api::RTKitProxyBlocking::builder(&connection)
         .cache_properties(zbus::proxy::CacheProperties::No)
         .build()?;
 
-    let max_realtime_priority = proxy.max_realtime_priority()?;
-    debug_assert!(
-        (0..=99).contains(&max_realtime_priority),
-        "max_realtime_priority must be between 0 and 99"
-    );
-    let priority = priority.unwrap_or(max_realtime_priority as u32);
+    let max_priority = proxy.max_realtime_priority()?;
+    let max_priority = max_priority
+        .try_into()
+        .map_err(|_| Error::InvalidMaxPriority(max_priority))?;
+    let priority = priority.unwrap_or_default().min(max_priority);
 
     proxy
-        .make_thread_realtime_with_pid(pid, tid, priority)
+        .make_thread_realtime_with_pid(pid, tid, priority.value())
         .map(|_| priority)
         .map_err(|e| match e {
             zbus::fdo::Error::AccessDenied(_) => Error::PermissionDenied,
             e => Error::ZbusMethodError(e),
         })
 }
+
+/// Helper for [set_thread_nice_level], uses the current thread's tid.
+pub fn set_current_thread_nice_level(nice_level: Option<NiceLevel>) -> Result<NiceLevel, Error> {
+    let thread_id = nix::unistd::gettid().as_raw().try_into().unwrap();
+    set_thread_nice_level(thread_id, nice_level)
+}
+
+/// Elevates the nice level of a thread as close as possible to the requested nice level.
+///
+/// If no nice level is specified, the maximum nice level allowed by the system will be used.
+///
+/// Returns the actual nice level that was set.
+pub fn set_thread_nice_level(tid: u64, nice_level: Option<NiceLevel>) -> Result<NiceLevel, Error> {
+    let connection = zbus::blocking::Connection::system()?;
+    let proxy = low_level_zbus_api::RTKitProxyBlocking::builder(&connection)
+        .cache_properties(zbus::proxy::CacheProperties::No)
+        .build()?;
+
+    let nice_level = nice_level.unwrap_or_default();
+
+    let max_nice_level = proxy.min_nice_level()?;
+    let max_nice_level = max_nice_level
+        .try_into()
+        .map_err(|_| Error::InvalidMinNiceLevel(max_nice_level))?;
+    let nice_level = nice_level.max(max_nice_level);
+
+    proxy
+        .make_thread_high_priority(tid, nice_level.value())
+        .map(|_| nice_level)
+        .map_err(|e| match e {
+            zbus::fdo::Error::AccessDenied(_) => Error::PermissionDenied,
+            e => Error::ZbusMethodError(e),
+        })
+}
+
+/// Elevates the nice level of a specified processes thread as close as possible to the requested nice level.
+///
+/// If no nice level is specified, the maximum nice level allowed by the system will be used.
+/// Returns the actual nice level that was set.
+pub fn set_process_thread_nice_level(
+    pid: u64,
+    tid: u64,
+    nice_level: Option<NiceLevel>,
+) -> Result<NiceLevel, Error> {
+    let connection = zbus::blocking::Connection::system()?;
+    let proxy = low_level_zbus_api::RTKitProxyBlocking::builder(&connection)
+        .cache_properties(zbus::proxy::CacheProperties::No)
+        .build()?;
+
+    let nice_level = nice_level.unwrap_or_default();
+    let max_nice_level = proxy.min_nice_level()?;
+    let max_nice_level = max_nice_level
+        .try_into()
+        .map_err(|_| Error::InvalidMinNiceLevel(max_nice_level))?;
+    let nice_level = nice_level.max(max_nice_level);
+
+    proxy
+        .make_thread_high_priority_with_pid(pid, tid, nice_level.value())
+        .map(|_| nice_level)
+        .map_err(|e| match e {
+            zbus::fdo::Error::AccessDenied(_) => Error::PermissionDenied,
+            e => Error::ZbusMethodError(e),
+        })
+}
diff --git a/src/types.rs b/src/types.rs
new file mode 100644
index 0000000..460fe8c
--- /dev/null
+++ b/src/types.rs
@@ -0,0 +1,124 @@
+use std::ops::Deref;
+
+#[derive(Debug, Clone, Copy, PartialEq, Eq, Hash, PartialOrd, Ord)]
+pub struct Priority(u32);
+
+impl Priority {
+    pub const MIN: u32 = 0;
+    pub const MAX: u32 = 99;
+
+    /// Creates a new Priority, ensuring it is within valid bounds (0-99).
+    pub fn new(value: u32) -> Option<Self> {
+        if value <= Self::MAX {
+            Some(Priority(value))
+        } else {
+            None
+        }
+    }
+
+    /// Returns the underlying priority value.
+    pub fn value(&self) -> u32 {
+        self.0
+    }
+}
+
+impl From<Priority> for u32 {
+    fn from(priority: Priority) -> Self {
+        priority.0
+    }
+}
+
+impl TryFrom<u32> for Priority {
+    type Error = &'static str;
+
+    fn try_from(value: u32) -> Result<Self, Self::Error> {
+        Priority::new(value).ok_or("Priority must be between 0 and 99")
+    }
+}
+
+impl TryFrom<i32> for Priority {
+    type Error = &'static str;
+
+    fn try_from(value: i32) -> Result<Self, Self::Error> {
+        if value < 0 {
+            return Err("Priority must be between 0 and 99");
+        }
+        Priority::new(value as u32).ok_or("Priority must be between 0 and 99")
+    }
+}
+
+impl Default for Priority {
+    fn default() -> Self {
+        Priority(99)
+    }
+}
+
+impl AsRef<u32> for Priority {
+    fn as_ref(&self) -> &u32 {
+        &self.0
+    }
+}
+
+impl Deref for Priority {
+    type Target = u32;
+
+    fn deref(&self) -> &Self::Target {
+        &self.0
+    }
+}
+
+#[derive(Debug, Clone, Copy, PartialEq, Eq, Hash, PartialOrd, Ord)]
+pub struct NiceLevel(i32);
+
+impl NiceLevel {
+    pub const MIN: i32 = -20;
+    pub const MAX: i32 = 19;
+
+    /// Creates a new NiceLevel, ensuring it is within valid bounds (-20 to 19).
+    pub fn new(value: i32) -> Option<Self> {
+        if (Self::MIN..=Self::MAX).contains(&value) {
+            Some(NiceLevel(value))
+        } else {
+            None
+        }
+    }
+
+    /// Returns the underlying nice level value.
+    pub fn value(&self) -> i32 {
+        self.0
+    }
+}
+
+impl From<NiceLevel> for i32 {
+    fn from(nice_level: NiceLevel) -> Self {
+        nice_level.0
+    }
+}
+
+impl TryFrom<i32> for NiceLevel {
+    type Error = &'static str;
+
+    fn try_from(value: i32) -> Result<Self, Self::Error> {
+        NiceLevel::new(value).ok_or("NiceLevel must be between -20 and 19")
+    }
+}
+
+impl Default for NiceLevel {
+    fn default() -> Self {
+        NiceLevel(Self::MIN)
+    }
+}
+
+impl AsRef<i32> for NiceLevel {
+    fn as_ref(&self) -> &i32 {
+        &self.0
+    }
+}
+
+impl Deref for NiceLevel {
+    type Target = i32;
+
+    fn deref(&self) -> &Self::Target {
+        &self.0
+    }
+}