Medication Half-Life and Steady-State Planner

Plan half-life and steady state

See how long levels take to build after a start or dose change. Education only.

Step 1

If given a range, enter the midpoint.

Step 2

12 = twice daily, 24 = once daily.

Optional

Use your own unit (mg, mL, etc.).

4–5 is a common starting point.

Adjust anytime.

Updates table & chart.

Fill in Step 1 and Step 2, then tap See my timing.

Plain guide: what the planner shows and how to use it

Quick summary

Enter the elimination half-life (hours) and your dosing interval to see how fast levels rise toward steady state after a start or change. You’ll get milestone timings (90–99%), a daily progress table, a compact chart, and a simple taper-spacing idea. This is educational and not medical advice.

Steady state in one minute

With repeated doses, what you add and what you clear begin to balance. Half-life is the time for levels to fall by 50%. A practical rule: you’re very close to steady state after about five half-lives. Shorter half-life → faster; longer → slower.

How to use it

  • Type half-life (e.g., 12, 24, 36, 48 h) and your interval (e.g., 12 or 24 h).
  • Pick a preview window and press See my timing.
  • The chart pointer and the daily table sync to your preview day.

Reading the results

  • Milestones: hours and days for 90%, 95%, 97.5%, 99% to steady state.
  • Accumulation factor (R): how much higher average exposure is at steady state vs a single dose for your schedule.

Taper spacing helper

Spacing changes by ≈4–5 half-lives lets levels settle before the next step. The helper converts that spacing into days and prints step dates to discuss with your prescriber.

Reality checks

  • Active metabolites, organ function, interactions, and extended-release forms can shift timing.
  • Missed doses and timing swings change day-to-day levels.
  • Use this to understand the curve and prepare questions; follow your clinician’s advice.
Daily progress toward steady state
Day Time since start (h) % to steady state

Assumes simple first-order elimination and consistent dosing times.

References

For learning only. Always follow your prescriber’s guidance.

Medication half-life planner FAQs
How long to reach steady state?

About five half-lives under simple elimination. The results show hours and days for 90–99% milestones.

Does how often I take it change the timing?

Interval mainly changes peak–trough swings; time to steady state is driven by half-life.

What is the accumulation factor (R)?

How much higher average exposure is at steady state vs a single dose for your half-life and interval.

Is this medical advice?

No. It’s an educational planner to support a discussion with your clinician.