If you've decided on daily tadalafil, the next question is dose: 2.5mg or 5mg? Both are FDA-approved for daily ED use, but they're not interchangeable. Here's how to choose.
What the Numbers Mean
At steady state (after ~5 days of daily dosing), tadalafil 2.5mg produces average plasma concentrations roughly half those of 5mg. Both maintain therapeutic levels around the clock, but the 5mg dose provides more headroom — a higher baseline of PDE5 inhibition.
For reference, a single on-demand 20mg dose peaks at approximately 378 ng/mL but drops below therapeutic levels within 36 hours. Daily dosing trades peak height for consistency.
When 5mg Is the Better Choice
- You also have BPH symptoms. The dual FDA approval for ED + BPH is for 5mg daily only. The 2.5mg dose was not studied for BPH and is not approved for that indication.
- You need more robust ED coverage. Men with moderate-to-severe ED are more likely to achieve satisfactory response at 5mg than 2.5mg.
- You tolerate 5mg without side effects. If back pain, myalgia, headache, or flushing aren't issues at 5mg, there's no reason to use the lower dose.
When 2.5mg Makes Sense
- Mild ED. Men with mild erectile difficulty may find 2.5mg sufficient to restore function.
- Side effect sensitivity. If 5mg produces bothersome back pain or headache, stepping down to 2.5mg may maintain enough efficacy while reducing side effects.
- Cost consideration. In some formularies, the 2.5mg tablet is cheaper. If it works, why pay more?
- No BPH component. If urinary symptoms aren't an issue, you lose nothing by starting at the lower dose.
The Practical Approach
Most prescribers start at 5mg daily, particularly if BPH is present. If side effects are bothersome, step down to 2.5mg and reassess. Some men alternate — 5mg on days when sexual activity is planned, 2.5mg otherwise — though this isn't the standard recommendation (the whole point of daily dosing is consistency).
If 5mg daily doesn't provide adequate ED coverage, the next step isn't increasing the daily dose above 5mg — it's adding an on-demand PDE5 inhibitor (sildenafil 50–100mg) on top of the daily tadalafil for planned encounters. This combination is used in clinical practice, though it's off-label and should be discussed with your provider.