How much does liothyronine build up with daily dosing?

At steady state on a daily schedule, the model's level is about 4.13 times what one dose gives, and it swings about 1.28:1 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 liothyronine 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.

Liothyronine Half-Life: Peak and Steady State Chart

Q: When does liothyronine peak after a dose?

Blood levels peak about 2.5 hours after a dose by mouth, according to Jonklaas J et al. 2015. Individual timing varies with food, the amount and the person.

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

About 12.5 days of regular dosing at the same amount and interval, which is 5 half-lives. With a half-life of about 2.5 days, levels reach about 50% of steady state after 2.5 days and about 90% after 8.3 days. Changing the dose or interval starts a new climb toward a new steady state.

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

Roughly 5 half-lives, about 12.5 days, until about 97% has cleared in the model. Half is gone about 2.5 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: Liothyronine has a half-life of about 2.5 days (Cytomel (liothyronine sodium) label) and reaches steady state after about 12.5 days of regular dosing. Levels peak about 2.5 hours after a dose by mouth. On a daily schedule the model builds up to about 4.1× a single dose, with a peak-to-trough swing of about 1.28:1.

What do liothyronine levels look like with daily dosing?

The Cytomel label starts adults with hypothyroidism at 25 mcg once daily, with a usual maintenance dose of 25 to 75 mcg once daily. The chart holds 25 mcg once daily as an example; your dose depends on your labs and your prescriber. Source: Cytomel (liothyronine sodium) label. Bioavailability 95% as in the app. Dashed line: 5 half-lives. Change the amount or schedule in the calculator.

When does liothyronine peak after a dose?

Levels peak about 2.5 hours after a dose by mouth.

How long does liothyronine 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 2.5 days:

Time from the first dose to each share of steady state, liothyronine (half-life 2.5 days).
Share of steady state	Half-lives	Time
50%	1	2.5 days
75%	2	5 days
90%	3.3	8.3 days
97% (Dose Track's steady-state rule)	5	12.5 days

How much do liothyronine 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, liothyronine, in Dose Track's model.
Interval	Peak : trough	Build-up vs one dose
Daily	1.28 : 1	4.13×
Every other day	1.69 : 1	2.35×
Twice weekly	2.56 : 1	1.61×
Weekly	6.73 : 1	1.17×
Every 2 weeks	46.9 : 1	1.02×

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

How long does liothyronine stay in your system?

After the last dose, about half is gone every 2.5 days. After 5 half-lives, about 12.5 days, roughly 97% has cleared in the model.

Where do these numbers come from?

The FDA Cytomel label gives a biological half-life of about 2.5 days; Dose Track uses 60 hours. The Synthroid label lists the T3 half-life as 2 days or less. The Cytomel label gives no time to peak; it says about 95% is absorbed within 4 hours. In single-dose studies T3 peaked 2.5 hours after 50 mcg (Jonklaas 2015) and 2.3 to 2.4 hours after 20 mcg (Leggio 2006); Dose Track uses 2.5 hours.

The curve uses the half-life, time to peak, route and bioavailability built into the Dose Track app for liothyronine, 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 Liothyronine guide.

When does liothyronine peak and reach steady state?