Check your empty slots first.

Probably. Most motherboards have four slots, so if you used two of them for your current 16GB (two 8GB sticks), you can add two more 8GB sticks to hit 32GB. If you used two 16GB sticks for your 16GB (that doesn’t add up—you’d be at 32GB already), or if your board only has two slots, you’ll need to replace.

The catch: mixing RAM kits isn’t guaranteed. Even if the specs match, different batches can be unstable. Ideally buy the exact same model. But in practice, same speed and timings usually work fine.

If you’re on a laptop? Almost certainly soldered or only two slots, so you’re replacing.

Worst case: it doesn’t POST and you return the new sticks. No permanent harm.