diff --git a/include/mbedtls/blowfish.h b/include/mbedtls/blowfish.h
index c0ef5a0..4b4916e 100644
--- a/include/mbedtls/blowfish.h
+++ b/include/mbedtls/blowfish.h
@@ -170,7 +170,24 @@
 /**
  * \brief               Blowfish-CTR buffer encryption/decryption
  *
- * Warning: You have to keep the maximum use of your counter in mind!
+ * \warning    You must never reuse a nonce value with the same key. Doing so
+ *             would void the encryption for the two messages encrypted with
+ *             the same nonce and key.
+ *
+ *             There are two common strategies for managing nonces with CTR:
+ *
+ *             1. Use a counter starting at 0 or a random value. With this
+ *             strategy, this function will increment the counter for you, so
+ *             you only need to preserve the \p nonce_counter buffer between
+ *             calls. With this strategy, you must not encrypt more than
+ *             2**64 blocks of data.
+ *             2. Use a randomly-generated \p nonce_counter for each call.
+ *             With this strategy, you need to ensure the nonce is generated
+ *             in an unbiased way and you must not encrypt more than 2**32
+ *             block of data.
+ *
+ *             Note that for both stategies, the limit is in number of blocks
+ *             and that a Blowfish block is 8 bytes.
  *
  * \param ctx           Blowfish context
  * \param length        The length of the data