diff --git a/R/compute.R b/R/compute.R
index 241fe1c..70074fe 100644
--- a/R/compute.R
+++ b/R/compute.R
@@ -1385,7 +1385,7 @@ compute_exposure_predictions <- function(
 
   if (!rlang::is_empty(cmaxes)) {
     new_conc <- c(prediction_df$conc, cmaxes)
-    prediction_df <- tibble::tibble(conc = sort(new_conc))
+    prediction_df <- tibble::tibble(conc = sort(unique(new_conc)))
   }
 
   ########## SHOULD THIS BE ITS OWN FUNCTION? ############
diff --git a/tests/testthat/test-compute_exposure_predictions.R b/tests/testthat/test-compute_exposure_predictions.R
index a407742..04d86a9 100644
--- a/tests/testthat/test-compute_exposure_predictions.R
+++ b/tests/testthat/test-compute_exposure_predictions.R
@@ -32,3 +32,42 @@ test_that('compute_exposure_predictions runs fine for good model and full data',
     )
   )
 })
+
+
+test_that('compute_exposure_predictions does not add non-unique conc values with cmaxes', {
+  data_proc <- preprocess(cqtkit_data_dofetilide)
+  mod <- fit_prespecified_model(
+    data_proc,
+    deltaQTCF,
+    ID,
+    CONC,
+    deltaQTCFBL,
+    TRTG,
+    TAFD,
+    method = "ML",
+    remove_conc_iiv = TRUE
+  )
+
+  expo_pred <- compute_exposure_predictions(
+    data_proc,
+    mod,
+    CONC,
+    treatment_predictors = list(
+      CONC = 10,
+      deltaQTCFBL = 0,
+      TRTG = "Dofetilide",
+      TAFD = "1 HR"
+    ),
+    control_predictors = list(
+      CONC = 0,
+      deltaQTCFBL = 0,
+      TRTG = "Placebo",
+      TAFD = "1 HR"
+    ),
+    cmaxes = c(100, 200, 300)
+  )
+
+  expect_true(
+    expo_pred$conc |> length() == expo_pred$conc |> unique() |> length()
+  )
+})