Styling post according if it contains a tag

Hello,

I am trying to figure out a way to insert some text into a post through the loop if the post has been assigned a specific tag. This is for the main index and single page (index.php) and not a tag/archive/category page.
The basic structure of what I have in mind is as follows:

<?php if(have_posts()) : ?>
<?php while(have_posts()) : the_post(); ?>
<div class="post-meta" id="post-<?php the_ID(); ?>">
<div class="post-content">

<strong><?php if (is_tag('11') ): ?>
Its alive...
<?php endif; ?></strong>
<?php the_content("Continue reading &rarr;"); ?>
</div>

What I need to understand is how can I make this work as the_tag() surely does not get the work done.

Any help would be appreciated.

Regards,

dheerg