diff --git a/app/lib/nhs/pds.rb b/app/lib/nhs/pds.rb
index 248289e78..1385f23c2 100644
--- a/app/lib/nhs/pds.rb
+++ b/app/lib/nhs/pds.rb
@@ -26,6 +26,9 @@ class InvalidNHSNumber < StandardError
   class PatientNotFound < StandardError
   end
 
+  class TooManyMatches < StandardError
+  end
+
   class << self
     def get_patient(nhs_number)
       NHS::API.connection.get(
@@ -54,10 +57,17 @@ def search_patients(attributes)
         raise "Unrecognised attributes: #{missing_attrs.join(", ")}"
       end
 
-      NHS::API.connection.get(
-        "personal-demographics/FHIR/R4/Patient",
-        attributes
-      )
+      response =
+        NHS::API.connection.get(
+          "personal-demographics/FHIR/R4/Patient",
+          attributes
+        )
+
+      if is_error?(response, "TOO_MANY_MATCHES")
+        raise TooManyMatches
+      else
+        response
+      end
     rescue Faraday::BadRequestError => e
       add_sentry_breadcrumb(e)
       raise
@@ -75,10 +85,17 @@ def add_sentry_breadcrumb(error)
       Sentry.add_breadcrumb(crumb)
     end
 
-    def is_error?(error, code)
-      response = JSON.parse(error.response_body)
+    def is_error?(error_or_response, code)
+      response =
+        if error_or_response.is_a?(Faraday::ClientError)
+          JSON.parse(error_or_response.response_body)
+        elsif error_or_response.is_a?(Faraday::Response)
+          error_or_response.body
+        end
+
+      return false if (issues = response["issue"]).blank?
 
-      response["issue"].any? do |issue|
+      issues.any? do |issue|
         issue["details"]["coding"].any? { |coding| coding["code"] == code }
       end
     end
diff --git a/spec/fixtures/files/pds/too-many-matches.json b/spec/fixtures/files/pds/too-many-matches.json
new file mode 100644
index 000000000..468363ce5
--- /dev/null
+++ b/spec/fixtures/files/pds/too-many-matches.json
@@ -0,0 +1,19 @@
+{
+  "issue": [
+    {
+      "code": "multiple-matches",
+      "details": {
+        "coding": [
+          {
+            "code": "TOO_MANY_MATCHES",
+            "display": "Too Many Matches",
+            "system": "https://fhir.nhs.uk/R4/CodeSystem/Spine-ErrorOrWarningCode",
+            "version": "1"
+          }
+        ]
+      },
+      "severity": "information"
+    }
+  ],
+  "resourceType": "OperationOutcome"
+}
diff --git a/spec/lib/nhs/pds_spec.rb b/spec/lib/nhs/pds_spec.rb
index d9969e417..ead873553 100644
--- a/spec/lib/nhs/pds_spec.rb
+++ b/spec/lib/nhs/pds_spec.rb
@@ -82,33 +82,61 @@
   end
 
   describe "#search_patients" do
-    before do
-      stub_request(
-        :get,
-        "https://sandbox.api.service.nhs.uk/personal-demographics/FHIR/R4/Patient"
-      ).with(
-        query: {
-          birthdate: "eq1939-01-09",
-          family: "Lawman",
-          gender: "female"
-        }
-      ).to_return(
-        body: file_fixture("pds/search-patients-response.json"),
-        headers: {
-          "Content-Type" => "application/fhir+json"
-        }
+    subject(:search_patients) do
+      described_class.search_patients(
+        family: "Lawman",
+        gender: "female",
+        birthdate: "eq1939-01-09"
       )
     end
 
-    it "sends a GET request to with the provided attributes" do
-      response =
-        described_class.search_patients(
-          family: "Lawman",
-          gender: "female",
-          birthdate: "eq1939-01-09"
+    context "with a successful response" do
+      before do
+        stub_request(
+          :get,
+          "https://sandbox.api.service.nhs.uk/personal-demographics/FHIR/R4/Patient"
+        ).with(
+          query: {
+            birthdate: "eq1939-01-09",
+            family: "Lawman",
+            gender: "female"
+          }
+        ).to_return(
+          body: file_fixture("pds/search-patients-response.json"),
+          headers: {
+            "Content-Type" => "application/fhir+json"
+          }
         )
+      end
+
+      it "sends a GET request to with the provided attributes" do
+        response = search_patients
+        expect(response.body).to include("total" => 1)
+      end
+    end
 
-      expect(response.body).to include("total" => 1)
+    context "with a too many matches response" do
+      before do
+        stub_request(
+          :get,
+          "https://sandbox.api.service.nhs.uk/personal-demographics/FHIR/R4/Patient"
+        ).with(
+          query: {
+            birthdate: "eq1939-01-09",
+            family: "Lawman",
+            gender: "female"
+          }
+        ).to_return(
+          body: file_fixture("pds/too-many-matches.json"),
+          headers: {
+            "Content-Type" => "application/fhir+json"
+          }
+        )
+      end
+
+      it "raises an error" do
+        expect { search_patients }.to raise_error(NHS::PDS::TooManyMatches)
+      end
     end
 
     it "raises an error if an unrecognised attribute is provided" do