diff --git a/include/mbedtls/ctr_drbg.h b/include/mbedtls/ctr_drbg.h
index 6c48ec1..7f1d232 100644
--- a/include/mbedtls/ctr_drbg.h
+++ b/include/mbedtls/ctr_drbg.h
@@ -210,6 +210,11 @@
  *                      and prepares it for mbedtls_ctr_drbg_seed()
  *                      or mbedtls_ctr_drbg_free().
  *
+ * \note                The reseed interval is
+ *                      #MBEDTLS_CTR_DRBG_RESEED_INTERVAL by default.
+ *                      You can override it by calling
+ *                      mbedtls_ctr_drbg_set_reseed_interval().
+ *
  * \param ctx           The CTR_DRBG context to initialize.
  */
 void mbedtls_ctr_drbg_init( mbedtls_ctr_drbg_context *ctx );
@@ -309,7 +314,8 @@
                    size_t len );
 
 /**
- * \brief               This function clears CTR_CRBG context data.
+ * \brief               This function resets CTR_DRBG context to the state immediately
+ *                      after initial call of mbedtls_ctr_drbg_init().
  *
  * \param ctx           The CTR_DRBG context to clear.
  */
diff --git a/include/mbedtls/hmac_drbg.h b/include/mbedtls/hmac_drbg.h
index 57ce9d9..9116541 100644
--- a/include/mbedtls/hmac_drbg.h
+++ b/include/mbedtls/hmac_drbg.h
@@ -111,6 +111,10 @@
  * This function makes the context ready for mbedtls_hmac_drbg_seed(),
  * mbedtls_hmac_drbg_seed_buf() or mbedtls_hmac_drbg_free().
  *
+ * \note                The reseed interval is #MBEDTLS_HMAC_DRBG_RESEED_INTERVAL
+ *                      by default. Override this value by calling
+ *                      mbedtls_hmac_drbg_set_reseed_interval().
+ *
  * \param ctx           HMAC_DRBG context to be initialized.
  */
 void mbedtls_hmac_drbg_init( mbedtls_hmac_drbg_context *ctx );
@@ -334,7 +338,8 @@
 int mbedtls_hmac_drbg_random( void *p_rng, unsigned char *output, size_t out_len );
 
 /**
- * \brief               Free an HMAC_DRBG context
+ * \brief               This function resets HMAC_DRBG context to the state immediately
+ *                      after initial call of mbedtls_hmac_drbg_init().
  *
  * \param ctx           The HMAC_DRBG context to free.
  */