diff --git a/code/modules/mob/living/carbon/monkey/monkey.dm b/code/modules/mob/living/carbon/monkey/monkey.dm
index 15ae5c68270..c8dd9a90e36 100644
--- a/code/modules/mob/living/carbon/monkey/monkey.dm
+++ b/code/modules/mob/living/carbon/monkey/monkey.dm
@@ -60,14 +60,13 @@
 
 /mob/living/carbon/monkey/on_reagent_change()
 	. = ..()
-	remove_movespeed_modifier(MOVESPEED_ID_MONKEY_REAGENT_SPEEDMOD, TRUE)
 	var/amount
 	if(reagents.has_reagent(/datum/reagent/medicine/morphine))
 		amount = -1
 	if(reagents.has_reagent(/datum/reagent/consumable/nuka_cola))
 		amount = -1
 	if(amount)
-		add_movespeed_modifier(MOVESPEED_ID_MONKEY_REAGENT_SPEEDMOD, TRUE, 100, override = TRUE, multiplicative_slowdown = amount)
+		add_or_update_movespeed_modifier(/datum/movespeed_modifier/variable/monkey_reagent_speedmod, TRUE, amount)
 
 /mob/living/carbon/monkey/updatehealth()
 	. = ..()
@@ -76,14 +75,14 @@
 		var/health_deficiency = (maxHealth - health)
 		if(health_deficiency >= 45)
 			slow += (health_deficiency / 25)
-	add_movespeed_modifier(MOVESPEED_ID_MONKEY_HEALTH_SPEEDMOD, TRUE, 100, override = TRUE, multiplicative_slowdown = slow)
+		add_or_update_movespeed_modifier(/datum/movespeed_modifier/variable/monkey_health_speedmod, TRUE, slow)
 
 /mob/living/carbon/monkey/adjust_bodytemperature(amount)
 	. = ..()
 	var/slow = 0
 	if (bodytemperature < 283.222)
 		slow += ((283.222 - bodytemperature) / 10) * 1.75
-	add_movespeed_modifier(MOVESPEED_ID_MONKEY_TEMPERATURE_SPEEDMOD, TRUE, 100, override = TRUE, multiplicative_slowdown = slow)
+		add_or_update_movespeed_modifier(/datum/movespeed_modifier/variable/monkey_temperature_speedmod, TRUE, slow)
 
 /mob/living/carbon/monkey/Stat()
 	..()
diff --git a/code/modules/mob/mob_movement.dm b/code/modules/mob/mob_movement.dm
index 98a59b851cd..4f49da4c02a 100644
--- a/code/modules/mob/mob_movement.dm
+++ b/code/modules/mob/mob_movement.dm
@@ -38,17 +38,17 @@
   * Move a client in a direction
   *
   * Huge proc, has a lot of functionality
-  * 
+  *
   * Mostly it will despatch to the mob that you are the owner of to actually move
   * in the physical realm
-  * 
+  *
   * Things that stop you moving as a mob:
   * * world time being less than your next move_delay
   * * not being in a mob, or that mob not having a loc
   * * missing the n and direction parameters
   * * being in remote control of an object (calls Moveobject instead)
   * * being dead (it ghosts you instead)
-  * 
+  *
   * Things that stop you moving as a mob living (why even have OO if you're just shoving it all
   * in the parent proc with istype checks right?):
   * * having incorporeal_move set (calls Process_Incorpmove() instead)
@@ -68,7 +68,7 @@
   *
   * Finally if you're pulling an object and it's dense, you are turned 180 after the move
   * (if you ask me, this should be at the top of the move so you don't dance around)
-  * 
+  *
   */
 /client/Move(n, direct)
 	if(world.time < move_delay) //do not move anything ahead of this check please
@@ -175,7 +175,7 @@
   * Allows mobs to ignore density and phase through objects
   *
   * Called by client/Move()
-  * 
+  *
   * The behaviour depends on the incorporeal_move value of the mob
   *
   * * INCORPOREAL_MOVE_BASIC - forceMoved to the next tile with no stop
@@ -263,9 +263,9 @@
   * Handles mob/living movement in space (or no gravity)
   *
   * Called by /client/Move()
-  * 
+  *
   * return TRUE for movement or FALSE for none
-  * 
+  *
   * You can move in space if you have a spacewalk ability
   */
 /mob/Process_Spacemove(movement_dir = 0)
@@ -443,7 +443,7 @@
 
 /**
   * Toggle the move intent of the mob
-  * 
+  *
   * triggers an update the move intent hud as well
   */
 /mob/proc/toggle_move_intent(mob/user)
diff --git a/code/modules/movespeed/_movespeed_modifier.dm b/code/modules/movespeed/_movespeed_modifier.dm
index 2df0435bfb5..a9315a4f9f9 100644
--- a/code/modules/movespeed/_movespeed_modifier.dm
+++ b/code/modules/movespeed/_movespeed_modifier.dm
@@ -63,14 +63,21 @@ GLOBAL_LIST_EMPTY(movespeed_modification_cache)
 /// Grabs a STATIC MODIFIER datum from cache. YOU MUST NEVER EDIT THESE DATUMS, OR IT WILL AFFECT ANYTHING ELSE USING IT TOO!
 /proc/get_cached_movespeed_modification(modtype)
 	if(!ispath(modtype, /datum/movespeed_modifier))
-		CRASH("[modtype] is not a movespeed modification type.")
+		CRASH("[modtype] is not a movespeed modification typepath.")
+	if(ispath(modtype, /datum/movespeed_modifier/variable))
+		CRASH("[modtype] is a variable modifier, and can never be cached.")
 	var/datum/movespeed_modifier/M = GLOB.movespeed_modification_cache[modtype] || ((GLOB.movespeed_modification_cache[modtype] = new modtype))
 	return M
 
-///Add a move speed modifier to a mob
+///Add a move speed modifier to a mob. If a variable subtype is passed in as the first argument, it will make a new datum.
 /mob/proc/_REFACTORING_add_movespeed_modifier(datum/movespeed_modifier/type_or_datum, update = TRUE, override = FALSE)
+	var/created = FALSE
 	if(ispath(type_or_datum))
-		type_or_datum = get_cached_movespeed_modification(type_or_datum)
+		if(!ispath(type_or_datum, /datum/movespeed_modifier/variable))
+			type_or_datum = get_cached_movespeed_modification(type_or_datum)
+		else
+			created = TRUE
+			type_or_datum = new type_or_datum
 	if(!istype(type_or_datum))
 		CRASH("Invalid modification datum")
 	var/oldpriority
@@ -79,19 +86,24 @@ GLOBAL_LIST_EMPTY(movespeed_modification_cache)
 		if(existing == type_or_datum)		//same thing don't need to touch
 			return TRUE
 		if(!override)						//not overriding, do not overwrite same ID.
+			if(created)			//make sure we clean up after ourselves.
+				qdel(type_or_datum)
 			return FALSE
 		oldpriority = existing.priority
-		remove_movespeed_modifier(existing, FLASE)
+		remove_movespeed_modifier(existing, FALSE)
 	LAZYSET(movespeed_modification, type_or_datum.id, type_or_datum)
 	var/resort = type_or_datum.priority == oldpriority
 	if(update)
 		update_movespeed(resort)
 	return TRUE
 
-///Remove a move speed modifier from a mob
+///Remove a move speed modifier from a mob, whether static or variable.
 /mob/proc/_REFACTORING_remove_movespeed_modifier(datum/movespeed_modifier/type_id_datum, update = TRUE)
 	if(ispath(type_id_datum))
-		type_id_datum = get_cached_movespeed_modification(type_id_datum)
+		if(!ispath(type_id_datum, /datum/movespeed_modifier/variable))
+			type_id_datum = get_cached_movespeed_modification(type_id_datum)
+		else
+			type_id_datum = initial(type_id_datum.id)
 	if(istype(type_id_datum))
 		type_id_datum = type_id_datum.id
 	if(!LAZYACCESS(movespeed_modification, type_id_datum))
@@ -102,6 +114,48 @@ GLOBAL_LIST_EMPTY(movespeed_modification_cache)
 		update_movespeed(FALSE)
 	return TRUE
 
+/// Used for variable slowdowns like hunger/health loss/etc, works somewhat like the old list-based modification adds.
+/// Implies override.
+/mob/proc/add_or_update_variable_movespeed_modifier(datum/movespeed_modifier/variable/type_id_datum, update = TRUE, multiplicative_slowdown)
+	/*
+	How this SHOULD work is:
+	1. Ensures type_id_datum one way or another refers to a /variable datum. This makes sure it can't be cached. This includes if it's already in the modification list.
+	2. Instantiate a new datum if type_id_datum isn't already instantiated + in the list, using the type. Obviously, wouldn't work for ID only.
+	3. Add the datum if necessary using the regular add proc
+	4. If any of the rest of the args are not null (see: multiplicative slowdown), modify the datum
+	5. Update if necessary
+	*/
+	. = FALSE
+	var/modified = FALSE
+	var/inject = FALSE
+	var/datum/movespeed_modifier/variable/final
+	if(istext(type_id_datum))
+		final = LAZYACCESS(movespeed_modification, type_id_datum)
+		if(!istype(final))
+			CRASH("Couldn't find existing modification when only provided an ID.")
+	else if(ispath(type_id_datum))
+		var/id = initial(type_id_datum.id)
+		final = LAZYACCESS(movespeed_modification, type_id_datum)
+		if(!istype(final))
+			final = new
+			inject = TRUE
+			modified = TRUE
+	else if(istype(type_id_datum))
+		final = type_id_datum
+		if(!LAZYACCESS(movespeed_modification, final.id))
+			inject = TRUE
+			modified = TRUE
+	else
+		CRASH("Invalid modifier")
+	if(!isnull(multiplicative_slowdown)
+		final.multiplicative_slowdown = multiplicative_slowdown
+		modified = TRUE
+	if(inject)
+		_REFACTORING_add_movespeed_modifier(final, FALSE, TRUE)
+	if(update && modified)
+		update_movespeed(TRUE)
+	return TRUE
+
 ///Handles the special case of editing the movement var
 /mob/vv_edit_var(var_name, var_value)
 	var/slowdown_edit = (var_name == NAMEOF(src, cached_multiplicative_slowdown))
@@ -164,13 +218,13 @@ GLOBAL_LIST_EMPTY(movespeed_modification_cache)
 /mob/proc/total_multiplicative_slowdown()
 	. = 0
 	for(var/id in get_movespeed_modifiers())
-		var/list/data = movespeed_modification[id]
-		. += data[MOVESPEED_DATA_INDEX_MULTIPLICATIVE_SLOWDOWN]
+		var/datum/movespeed_modifier/M = movespeed_modification[id]
+		. += M.multiplicative_slowdown()
 
 ///Checks if a move speed modifier is valid and not missing any data
-/proc/movespeed_data_null_check(list/data)		//Determines if a data list is not meaningful and should be discarded.
+/proc/movespeed_data_null_check(datum/movespeed_modifier/M)		//Determines if a data list is not meaningful and should be discarded.
 	. = TRUE
-	if(data[MOVESPEED_DATA_INDEX_MULTIPLICATIVE_SLOWDOWN])
+	if(M.multiplicative_slowdown)
 		. = FALSE
 
 /**
diff --git a/code/modules/movespeed/modifiers/variable.dm b/code/modules/movespeed/modifiers/variable.dm
new file mode 100644
index 00000000000..f7836a90c9e
--- /dev/null
+++ b/code/modules/movespeed/modifiers/variable.dm
@@ -0,0 +1,10 @@
+/datum/movespeed_modifier/variable
+
+/datum/movespeed_modifier/variable/monkey_reagent_speedmod
+	id = MOVESPEED_ID_MONKEY_REAGENT_SPEEDMOD
+
+/datum/movespeed_modifier/variable/monkey_health_speedmod
+	id = MOVESPEED_ID_MONKEY_HEALTH_SPEEDMOD
+
+/datum/movespeed_modifier/variable/monkey_temperature_speedmod
+	id = MOVESPEED_ID_MONKEY_TEMPERATURE_SPEEDMOD
diff --git a/tgstation.dme b/tgstation.dme
index e550eeec980..7642b2722b8 100644
--- a/tgstation.dme
+++ b/tgstation.dme
@@ -2383,6 +2383,7 @@
 #include "code\modules\movespeed\modifiers\innate.dm"
 #include "code\modules\movespeed\modifiers\reagent.dm"
 #include "code\modules\movespeed\modifiers\status_effects.dm"
+#include "code\modules\movespeed\modifiers\variable.dm"
 #include "code\modules\ninja\__ninjaDefines.dm"
 #include "code\modules\ninja\energy_katana.dm"
 #include "code\modules\ninja\ninja_event.dm"