diff --git a/async_postgres/pg_client.nim b/async_postgres/pg_client.nim
index 642a95e..5dfbd4f 100644
--- a/async_postgres/pg_client.nim
+++ b/async_postgres/pg_client.nim
@@ -1566,6 +1566,29 @@ proc hasReturnStmt*(n: NimNode): bool =
       return true
   return false
 
+proc buildTxBeginAndTimeout*(arg: NimNode): tuple[beginSql, txTimeout: NimNode] =
+  ## Shared helper for `withTransaction` macros.
+  ## Uses `when ... is` to dispatch on the argument type at compile time.
+  let buildBeginSqlSym = bindSym"buildBeginSql"
+  let zeroDurSym = bindSym"ZeroDuration"
+  let txOptsSym = bindSym"TransactionOptions"
+  let durSym = bindSym"Duration"
+  let beginSql = quote:
+    when `arg` is `txOptsSym`:
+      `buildBeginSqlSym`(`arg`)
+    elif `arg` is `durSym`:
+      "BEGIN"
+    else:
+      {.error: "withTransaction expects TransactionOptions or Duration".}
+  let txTimeout = quote:
+    when `arg` is `txOptsSym`:
+      `zeroDurSym`
+    elif `arg` is `durSym`:
+      `arg`
+    else:
+      {.error: "withTransaction expects TransactionOptions or Duration".}
+  (beginSql, txTimeout)
+
 macro withTransaction*(conn: PgConnection, args: varargs[untyped]): untyped =
   ## Execute `body` inside a BEGIN/COMMIT transaction.
   ## On exception, ROLLBACK is issued automatically.
@@ -1580,10 +1603,6 @@ macro withTransaction*(conn: PgConnection, args: varargs[untyped]): untyped =
   ##     await conn.exec(...)
   ##   conn.withTransaction(TransactionOptions(...), seconds(5)):
   ##     await conn.exec(...)
-  ##
-  ## **Note:** `TransactionOptions` must be passed as a constructor literal, not
-  ## through a variable (the macro uses AST node kind to distinguish options
-  ## from timeout).
   var body: NimNode
   var beginSql: NimNode
   var txTimeout: NimNode
@@ -1593,15 +1612,8 @@ macro withTransaction*(conn: PgConnection, args: varargs[untyped]): untyped =
     beginSql = newStrLitNode("BEGIN")
     txTimeout = bindSym"ZeroDuration"
   of 2:
-    if args[0].kind == nnkObjConstr:
-      # conn.withTransaction(TransactionOptions(...)): body
-      beginSql = newCall(bindSym"buildBeginSql", args[0])
-      txTimeout = bindSym"ZeroDuration"
-    else:
-      # conn.withTransaction(timeout): body
-      beginSql = newStrLitNode("BEGIN")
-      txTimeout = args[0]
     body = args[1]
+    (beginSql, txTimeout) = buildTxBeginAndTimeout(args[0])
   of 3:
     let opts = args[0]
     txTimeout = args[1]
diff --git a/async_postgres/pg_pool.nim b/async_postgres/pg_pool.nim
index 6b25f85..4de434b 100644
--- a/async_postgres/pg_pool.nim
+++ b/async_postgres/pg_pool.nim
@@ -641,10 +641,6 @@ macro withTransaction*(pool: PgPool, args: varargs[untyped]): untyped =
   ##   pool.withTransaction(conn, opts, seconds(5)):
   ##     conn.exec(...)
   ##
-  ## **Note:** `TransactionOptions` must be passed as a constructor literal, not
-  ## through a variable (the macro uses AST node kind to distinguish options
-  ## from timeout).
-  ##
   ## **Warning:** Inside the body, use `conn.exec(...)` / `conn.query(...)`
   ## directly — not `pool.exec(...)` / `pool.query(...)`. Pool methods acquire
   ## a separate connection, so those statements would run outside this transaction.
@@ -659,15 +655,8 @@ macro withTransaction*(pool: PgPool, args: varargs[untyped]): untyped =
     txTimeout = bindSym"ZeroDuration"
   of 3:
     connIdent = args[0]
-    if args[1].kind == nnkObjConstr:
-      # pool.withTransaction(conn, TransactionOptions(...)): body
-      beginSql = newCall(bindSym"buildBeginSql", args[1])
-      txTimeout = bindSym"ZeroDuration"
-    else:
-      # pool.withTransaction(conn, timeout): body
-      beginSql = newStrLitNode("BEGIN")
-      txTimeout = args[1]
     body = args[2]
+    (beginSql, txTimeout) = buildTxBeginAndTimeout(args[1])
   of 4:
     connIdent = args[0]
     let opts = args[1]
diff --git a/tests/test_e2e.nim b/tests/test_e2e.nim
index f61b57f..e80e932 100644
--- a/tests/test_e2e.nim
+++ b/tests/test_e2e.nim
@@ -1053,6 +1053,101 @@ suite "E2E: Transaction":
 
     waitFor t()
 
+  test "withTransaction with TransactionOptions variable":
+    proc t() {.async.} =
+      let conn = await connect(plainConfig())
+      discard await conn.exec("DROP TABLE IF EXISTS test_tx_opts_var")
+      discard await conn.exec(
+        "CREATE TABLE test_tx_opts_var (id serial PRIMARY KEY, val text)"
+      )
+
+      let opts = TransactionOptions(isolation: ilSerializable)
+      conn.withTransaction(opts):
+        discard await conn.exec(
+          "INSERT INTO test_tx_opts_var (val) VALUES ($1)", @[toPgParam("opts_var")]
+        )
+
+      let res = await conn.query("SELECT val FROM test_tx_opts_var")
+      doAssert res.rows.len == 1
+      doAssert res.rows[0].getStr(0) == "opts_var"
+
+      discard await conn.exec("DROP TABLE test_tx_opts_var")
+      await conn.close()
+
+    waitFor t()
+
+  test "withTransaction with Duration variable":
+    proc t() {.async.} =
+      let conn = await connect(plainConfig())
+      discard await conn.exec("DROP TABLE IF EXISTS test_tx_dur_var")
+      discard await conn.exec(
+        "CREATE TABLE test_tx_dur_var (id serial PRIMARY KEY, val text)"
+      )
+
+      let timeout = seconds(5)
+      conn.withTransaction(timeout):
+        discard await conn.exec(
+          "INSERT INTO test_tx_dur_var (val) VALUES ($1)", @[toPgParam("dur_var")]
+        )
+
+      let res = await conn.query("SELECT val FROM test_tx_dur_var")
+      doAssert res.rows.len == 1
+      doAssert res.rows[0].getStr(0) == "dur_var"
+
+      discard await conn.exec("DROP TABLE test_tx_dur_var")
+      await conn.close()
+
+    waitFor t()
+
+  test "pool.withTransaction with TransactionOptions variable":
+    proc t() {.async.} =
+      let pool =
+        await newPool(PoolConfig(connConfig: plainConfig(), minSize: 1, maxSize: 3))
+      discard await pool.exec("DROP TABLE IF EXISTS test_ptx_opts_var")
+      discard await pool.exec(
+        "CREATE TABLE test_ptx_opts_var (id serial PRIMARY KEY, val text)"
+      )
+
+      let opts = TransactionOptions(isolation: ilRepeatableRead)
+      pool.withTransaction(conn, opts):
+        discard await conn.exec(
+          "INSERT INTO test_ptx_opts_var (val) VALUES ($1)",
+          @[toPgParam("pool_opts_var")],
+        )
+
+      let res = await pool.query("SELECT val FROM test_ptx_opts_var")
+      doAssert res.rows.len == 1
+      doAssert res.rows[0].getStr(0) == "pool_opts_var"
+
+      discard await pool.exec("DROP TABLE test_ptx_opts_var")
+      await pool.close()
+
+    waitFor t()
+
+  test "pool.withTransaction with Duration variable":
+    proc t() {.async.} =
+      let pool =
+        await newPool(PoolConfig(connConfig: plainConfig(), minSize: 1, maxSize: 3))
+      discard await pool.exec("DROP TABLE IF EXISTS test_ptx_dur_var")
+      discard await pool.exec(
+        "CREATE TABLE test_ptx_dur_var (id serial PRIMARY KEY, val text)"
+      )
+
+      let timeout = seconds(5)
+      pool.withTransaction(conn, timeout):
+        discard await conn.exec(
+          "INSERT INTO test_ptx_dur_var (val) VALUES ($1)", @[toPgParam("pool_dur_var")]
+        )
+
+      let res = await pool.query("SELECT val FROM test_ptx_dur_var")
+      doAssert res.rows.len == 1
+      doAssert res.rows[0].getStr(0) == "pool_dur_var"
+
+      discard await pool.exec("DROP TABLE test_ptx_dur_var")
+      await pool.close()
+
+    waitFor t()
+
   test "withSavepoint releases on success":
     proc t() {.async.} =
       let conn = await connect(plainConfig())