How much does anastrozole build up with daily dosing?

At steady state on a daily schedule, the model's level is about 3.41 times what one dose gives, and it swings about 1.38:1 between the peak and the trough before the next dose. Longer gaps between doses mean less build-up and a bigger swing.

Is this chart my actual anastrozole level?

No. It is a modeled estimate from a published half-life, using the same one-compartment model as the Dose Track app. Real levels vary with body weight, food, kidney and liver function and other factors, and only a lab test measures them. It is not medical advice.

Anastrozole Half-Life: Peak and Steady State Chart

Q: When does anastrozole peak after a dose?

Blood levels peak about 2 hours after a dose by mouth, according to Arimidex (anastrozole) label. Individual timing varies with food, the amount and the person.

Q: How long does anastrozole take to reach steady state?

About 10 days of regular dosing at the same amount and interval, which is 5 half-lives. With a half-life of about 2 days, levels reach about 50% of steady state after 2 days and about 90% after 6.6 days. Changing the dose or interval starts a new climb toward a new steady state.

Q: How long does anastrozole stay in your system after the last dose?

Roughly 5 half-lives, about 10 days, until about 97% has cleared in the model. Half is gone about 2 days after levels start falling. Real clearance varies from person to person, and a drug can still have effects after levels are low.

Short answer: Anastrozole has a half-life of about 2 days (Arimidex (anastrozole) label) and reaches steady state after about 10 days of regular dosing. Levels peak about 2 hours after a dose by mouth. On a daily schedule the model builds up to about 3.4× a single dose, with a peak-to-trough swing of about 1.38:1.

What do anastrozole levels look like with daily dosing?

The Arimidex label dose is 1 mg once daily (postmenopausal breast cancer); the label says plasma levels approach steady state at about 7 days. Use in men on TRT is off-label. Source: Arimidex (anastrozole) label. Bioavailability 85% as in the app. Dashed line: 5 half-lives. Change the amount or schedule in the calculator.

When does anastrozole peak after a dose?

Levels peak about 2 hours after a dose by mouth.

How long does anastrozole take to reach steady state?

With regular dosing at a fixed amount and interval, levels climb toward steady state by the same fraction every half-life, whatever the dose. At a half-life of about 2 days:

Time from the first dose to each share of steady state, anastrozole (half-life 2 days).
Share of steady state	Half-lives	Time
50%	1	2 days
75%	2	4 days
90%	3.3	6.6 days
97% (Dose Track's steady-state rule)	5	10 days

How much do anastrozole levels swing between doses?

The longer the gap between doses compared with the half-life, the bigger the swing from peak to trough and the less the levels build up. These ratios do not depend on the amount.

Steady-state peak:trough and build-up by dosing interval, anastrozole, in Dose Track's model.
Interval	Peak : trough	Build-up vs one dose
Daily	1.38 : 1	3.41×
Every other day	1.94 : 1	2×
Twice weekly	3.26 : 1	1.42×
Weekly	10.9 : 1	1.1×
Every 2 weeks	124 : 1	1.01×

Build-up is the accumulation ratio 1 / (1 − e^−k·τ), with k = ln 2 / half-life and τ the interval.

How long does anastrozole stay in your system?

After the last dose, about half is gone every 2 days. After 5 half-lives, about 10 days, roughly 97% has cleared in the model.

Where do these numbers come from?

The FDA Arimidex label gives a mean elimination half-life of 50 hours; Dose Track uses 48 hours. Peak levels typically occur within 2 hours of a dose on an empty stomach (about 5 hours if taken after a meal, with the same total absorption), and steady state is reached after about 7 days of once-daily dosing.

Arimidex (anastrozole) prescribing information, sections 1, 2 and 12.3. DailyMed, revised 12/2025.

The curve uses the half-life, time to peak, route and bioavailability built into the Dose Track app for anastrozole, and the same one-compartment model with first-order absorption. These are modeled estimates from published half-lives, drawn with the same one-compartment model as the Dose Track app. Real levels vary from person to person, and only a lab test measures them. This is not medical advice and not a dosing recommendation; dosing decisions belong with you and your prescriber.

Vial sizes and syringe math are in the Anastrozole guide.

When does anastrozole peak and reach steady state?