diff --git a/src/fetch-api.ts b/src/fetch-api.ts
index 5b14abb..fe099bd 100644
--- a/src/fetch-api.ts
+++ b/src/fetch-api.ts
@@ -1,8 +1,13 @@
 import ky from 'ky';
+import type { Options } from 'ky';
 import { OpenAIApiError } from './errors';
 
 const DEFAULT_BASE_URL = 'https://api.openai.com/v1';
 
+export interface FetchOptions extends Options {
+  credentials?: string;
+}
+
 /**
  * Create an instance of Ky with options shared by all requests.
  */
@@ -10,6 +15,7 @@ export function createApiInstance(opts: {
   apiKey: string;
   baseUrl?: string;
   organizationId?: string;
+  fetchOptions?: FetchOptions;
 }) {
   return ky.extend({
     prefixUrl: opts.baseUrl || DEFAULT_BASE_URL,
@@ -21,6 +27,7 @@ export function createApiInstance(opts: {
         'OpenAI-Organization': opts.organizationId,
       }),
     },
+    ...opts.fetchOptions,
     hooks: {
       beforeError: [
         // @ts-ignore
diff --git a/src/openai-client.ts b/src/openai-client.ts
index bf65f7d..3172970 100644
--- a/src/openai-client.ts
+++ b/src/openai-client.ts
@@ -8,6 +8,7 @@ import type {
 } from './schemas/completion';
 import type { EditParams, EditResponse } from './schemas/edit';
 import type { EmbeddingParams, EmbeddingResponse } from './schemas/embedding';
+import type { FetchOptions } from './fetch-api';
 
 export type ConfigOpts = {
   /**
@@ -25,6 +26,8 @@ export type ConfigOpts = {
    * @see https://beta.openai.com/docs/api-reference/requesting-organization
    */
   organizationId?: string;
+
+  fetchOptions?: FetchOptions;
 };
 
 export class OpenAIClient {
@@ -39,6 +42,7 @@ export class OpenAIClient {
     this.api = createApiInstance({
       apiKey,
       organizationId: opts.organizationId,
+      fetchOptions: opts.fetchOptions,
     });
   }