People often search for an exact step count, but the physical experience is more useful to know. The descent is hundreds of narrow steps down a spiral staircase, and the exact route can vary with the tower and operating arrangements, so we would not choose a tower on the strength of an online step count.
Ask yourself instead: am I comfortable walking down a long, narrow spiral staircase with no lift option back down? If the answer is no, skip the tower.
For most healthy visitors the staircase is not scary, but it can be uncomfortable if you dislike heights, narrow stairs, enclosed spaces, looking down through a spiral or long descents. The official conditions exclude visitors with vertigo, claustrophobia or a tendency to dizziness for safety reasons. That is a stronger warning than you'll see at most viewpoints, so take it seriously.
Is there a handrail?
There is hand support on suitable sections, but this is still an old-style tower descent, not a broad accessible stairway. Wear shoes you are comfortable walking downstairs in, and leave behind unstable heels, footwear that slips easily and anything that makes you nervous on narrow steps.
Is the spiral staircase open in the middle?
Some sections have a central void, which creates the swirling view often seen in Sagrada Família tower photos. If looking down a stairwell triggers vertigo, think about that before booking: the thing photographers love is the same thing that makes the descent unpleasant for someone uneasy with heights.