diff --git a/src/Library/GrowthRates/GrowthRateLibrary.cpp b/src/Library/GrowthRates/GrowthRateLibrary.cpp
index f6383df..cb46eb5 100644
--- a/src/Library/GrowthRates/GrowthRateLibrary.cpp
+++ b/src/Library/GrowthRates/GrowthRateLibrary.cpp
@@ -1,11 +1,31 @@
 #include "GrowthRateLibrary.hpp"
+#include <algorithm>
+#include "../../Core/Exceptions/CreatureException.hpp"
 
 uint8_t CreatureLib::Library::GrowthRateLibrary::CalculateLevel(const std::string& growthRate,
                                                                 uint32_t experience) const {
-    return _growthRates.at(growthRate)->CalculateLevel(experience);
+    auto g = growthRate;
+    std::transform(g.begin(), g.end(), g.begin(), ::tolower);
+    auto find = _growthRates.find(g);
+    if (find == _growthRates.end()) {
+        throw CreatureException("Invalid growth rate was requested.");
+    }
+    return find->second->CalculateLevel(experience);
 }
 
 uint32_t CreatureLib::Library::GrowthRateLibrary::CalculateExperience(const std::string& growthRate,
                                                                       uint8_t level) const {
-    return _growthRates.at(growthRate)->CalculateExperience(level);
+    auto g = growthRate;
+    std::transform(g.begin(), g.end(), g.begin(), ::tolower);
+    auto find = _growthRates.find(g);
+    if (find == _growthRates.end()) {
+        throw CreatureException("Invalid growth rate was requested.");
+    }
+    return find->second->CalculateExperience(level);
+}
+void CreatureLib::Library::GrowthRateLibrary::AddGrowthRate(const std::string& name,
+                                                            CreatureLib::Library::GrowthRate* rate) {
+    auto g = name;
+    std::transform(g.begin(), g.end(), g.begin(), ::tolower);
+    _growthRates.insert({g, rate});
 }
diff --git a/src/Library/GrowthRates/GrowthRateLibrary.hpp b/src/Library/GrowthRates/GrowthRateLibrary.hpp
index 4092e66..21fccf9 100644
--- a/src/Library/GrowthRates/GrowthRateLibrary.hpp
+++ b/src/Library/GrowthRates/GrowthRateLibrary.hpp
@@ -24,7 +24,7 @@ namespace CreatureLib::Library {
         [[nodiscard]] uint8_t CalculateLevel(const std::string& growthRate, uint32_t experience) const;
         [[nodiscard]] uint32_t CalculateExperience(const std::string& growthRate, uint8_t level) const;
 
-        void AddGrowthRate(std::string name, GrowthRate* rate) { _growthRates.insert({name, rate}); }
+        void AddGrowthRate(const std::string& name, GrowthRate* rate);
     };
 }