diff --git a/include/mbedtls/mbedtls_config.h b/include/mbedtls/mbedtls_config.h
index f467737..18dbcd1 100644
--- a/include/mbedtls/mbedtls_config.h
+++ b/include/mbedtls/mbedtls_config.h
@@ -2807,6 +2807,9 @@
  * Can significantly increase throughput on systems without GCM hardware
  * acceleration (e.g., AESNI, AESCE).
  *
+ * The mbedtls_gcm_context size will increase by 3840 bytes.
+ * The code size will increase by roughly 344 bytes.
+ *
  * Module:  library/gcm.c
  *
  * Requires: MBEDTLS_GCM_C