<form action="sady_zooSQL.php" method="get">
  <select name="Ošetřovatel">
    <?php $dotaz = "SELECT IDo, Krestni, Prijmeni FROM Osetrovatel";
          $vysledekdotazu = mysqli_query ($dblink, $dotaz);

          while ($radek = mysqli_fetch_assoc ($vysledekdotazu)) {
            echo "{$radek[""]} {$radek[""]}";
          }
    ?>
      <option value="<?php echo "{$dotaz[""]}"; ?>"> <?php echo "{$dotaz[""]}"; ?>" </option>
  </select>
  <input type="submit" value="potvrdit" />
</form>