diff --git a/R/convert_conc_unit.R b/R/convert_conc_unit.R
index 4208dd8..8786252 100644
--- a/R/convert_conc_unit.R
+++ b/R/convert_conc_unit.R
@@ -31,14 +31,22 @@ convert_conc_unit <- function(value, unit_in, unit_out, mol_weight = NULL) {
     `g/l`        = 1000000,
     mg_dl        = 10000,
     `mg/dl`      = 10000,
+    mg_l         = 1000,
+    `mg/l`       = 1000,
+    pg_ml        = 1e-3,
+    `pg/ml`      = 1e-3,
     `micromol/l` = mol_weight,
     micromol_l   = mol_weight,
     micromol     = mol_weight,
-    mmol         = mol_weight,
+    mmol         = mol_weight * 1000,
+    mmol_l       = mol_weight * 1000,
+    `mmol/l`     = mol_weight * 1000,
     `mumol/l`    = mol_weight,
     `umol/l`     = mol_weight,
     mumol_l      = mol_weight,
-    umol_l       = mol_weight
+    umol_l       = mol_weight,
+    pmol_l       = mol_weight * 1e-6,
+    `pmol/l`     = mol_weight * 1e-6
   )
 
   unit_out <- match.arg(unit_out, names(conv))
diff --git a/tests/testthat/test_convert_conc_unit.R b/tests/testthat/test_convert_conc_unit.R
index 6424782..fb8beac 100644
--- a/tests/testthat/test_convert_conc_unit.R
+++ b/tests/testthat/test_convert_conc_unit.R
@@ -5,6 +5,8 @@ test_that("convert_conc_unit can convert g/dl, g/l, mg/dl", {
   expect_equal(convert_conc_unit(1, "mg_dl", "g_dl")$value, .001)
   expect_equal(convert_conc_unit(1, "mg_dl", "g_l")$value, 0.01)
   expect_equal(convert_conc_unit(1, "g_l", "mg_dl")$value, 100)
+  expect_equal(convert_conc_unit(1, "g_l", "mg_l")$value, 1000)
+  expect_equal(convert_conc_unit(1, "mg_l", "pg_ml")$value, 1e6)
 })
 
 test_that("molecular weight required when converting molar units", {
@@ -17,6 +19,8 @@ test_that("molecular weight required when converting molar units", {
 
 test_that("molar unit conversion works", {
   expect_equal(convert_conc_unit(1, "mg_dl", "micromol_l", 0.5)$value, 20000)
+  expect_equal(convert_conc_unit(200, "pg_ml", "pmol_l", 50)$value, 4000)
+  expect_equal(convert_conc_unit(1, "mmol_l", "pmol_l", 17)$value, 1e9)
 })
 
 test_that("vectorized input works", {