diff --git a/R/ard_categorical.survey.design.R b/R/ard_categorical.survey.design.R
index 1827970e..63cb9b0c 100644
--- a/R/ard_categorical.survey.design.R
+++ b/R/ard_categorical.survey.design.R
@@ -117,6 +117,15 @@ ard_categorical.survey.design <- function(data,
     }
   )
 
+  # return note about column names that result in errors -----------------------
+  if (any(by %in% c("variable", "variable_level"))) {
+    cli::cli_abort(
+      "The {.arg by} argument cannot include variables named {.val {c('variable', 'variable_level')}}.",
+      call = get_cli_abort_call()
+    )
+  }
+
+
   # calculate counts -----------------------------------------------------------
   # this tabulation accounts for unobserved combinations
   svytable_counts <- .svytable_counts(data, variables, by, denominator)
diff --git a/tests/testthat/_snaps/ard_categorical.survey.design.md b/tests/testthat/_snaps/ard_categorical.survey.design.md
index c72bebd0..55c7abb1 100644
--- a/tests/testthat/_snaps/ard_categorical.survey.design.md
+++ b/tests/testthat/_snaps/ard_categorical.survey.design.md
@@ -28,3 +28,11 @@
       ! Column "Class" is all missing and cannot be tabulated.
       i Only columns of class <logical> and <factor> can be tabulated when all values are missing.
 
+# ard_categorical.survey.design(by) messages about protected names
+
+    Code
+      ard_categorical(svy_mtcars, by = variable, variables = gear)
+    Condition
+      Error in `ard_categorical()`:
+      ! The `by` argument cannot include variables named "variable" and "variable_level".
+
diff --git a/tests/testthat/test-ard_categorical.survey.design.R b/tests/testthat/test-ard_categorical.survey.design.R
index 7ba6333e..68003272 100644
--- a/tests/testthat/test-ard_categorical.survey.design.R
+++ b/tests/testthat/test-ard_categorical.survey.design.R
@@ -1172,3 +1172,29 @@ test_that("ard_categorical.survey.design() works with variables with only 1 leve
   )
   expect_invisible(cards::check_ard_structure(ard_svy_cat_cell, method = FALSE))
 })
+
+
+test_that("ard_categorical.survey.design(by) messages about protected names", {
+  svy_mtcars <-
+    survey::svydesign(
+      ids = ~1,
+      data = mtcars |>
+        dplyr::mutate(
+          variable = am,
+          variable_level = cyl,
+          by = am,
+          by_level = cyl
+        ),
+      weights = ~1
+    )
+
+  expect_snapshot(
+    error = TRUE,
+    ard_categorical(svy_mtcars, by = variable, variables = gear)
+  )
+
+  expect_error(
+    ard_categorical(svy_mtcars, by = variable_level, variables = gear),
+    'The `by` argument cannot include variables named "variable" and "variable_level".'
+  )
+})