WP $current.user

i am trying to grabb some data and only show data that have the same value as the current user

iam using the plugin php insert

the code i am using

$sql = "SELECT * FROM Medlemar Where Medl_nr= . $current_user->Medl_nr% .";

Medl_nr is a custom field in wp.users table i created

and with $current_user->Medl_nr is giving me the value if i run the code seperat.

but running the query then i am only getting 0 result.
soo it seem like the query can′t get the current_user data (that should be a number and in this case it is number 25)

soo am i doing something wrong or am i missing something

all the code i am using

[insert_php]

$servername = "db host";
$username = "user";
$password = "pass";
$dbname = "db_1";

// Create connection
$conn = mysqli_connect($servername, $username, $password, $dbname);
// Check connection
if (!$conn) {
    die("Connection failed: " . mysqli_connect_error());
}
$sql = "SELECT * FROM Medlemar Where Medl_nr= . $current_user->Medl_nr% .";
$result = $conn->query($sql);

if ($result->num_rows > 0) {
    // output data of each row
    while($row = $result->fetch_assoc()) {
  echo "Medl_nr: " . $row['Medl_nr']. " - Namn: " . $row["namn"]. " " . $row["efternamn"]. "<br>";;
    }
} else {
    echo "0 results";
}
$conn->close();

[/insert_php]

the wp db and the db1 i am trying to get data from is on diffrent servers.