Teriparatide is the drug version of the first 34 amino acids of human parathyroid hormone, the fragment that carries the hormone's activity. Given once a day, it stimulates new bone formation; its label describes the effect as anabolic. It has been an approved medicine in the US since 2002, with one labelled dose, a pen designed around that dose, and a two-decade trial record. It now also appears on research-peptide price lists, as a powder in a vial, which is where the arithmetic starts to matter.
The label
FORTEO, Eli Lilly, NDA 021318, first approved 2002-11-26; label effective 2026-08-03 on openFDA. Three indications:
- postmenopausal women with osteoporosis at high risk of fracture, or who have failed or cannot tolerate other treatment;
- men with primary or hypogonadal osteoporosis at high risk of fracture, to increase bone mass;
- men and women with osteoporosis from sustained glucocorticoid use (5 mg a day of prednisone or equivalent).
| What the label states | |
|---|---|
| Dose | 20 mcg subcutaneously, once a day |
| Site | thigh or abdomen; not for intravenous or intramuscular use |
| First doses | where the patient can sit or lie down (orthostatic hypotension) |
| Supplements | calcium and vitamin D if dietary intake is inadequate |
| Pen | 560 mcg / 2.24 mL (250 mcg/mL), 28 doses of 20 mcg |
| Pen life | discard 28 days after first use; refrigerate 2–8 °C; never freeze |
| Duration | beyond 2 years in a lifetime only if fracture risk remains or returns high |
The dose is the same for men and women. The label notes that systemic exposure is 20–30% lower in men and keeps the dose unchanged anyway.
The pen arithmetic
At 250 mcg/mL, 20 mcg is 0.08 mL. The pen holds 560 mcg, which is exactly 28 doses; the 28-day discard rule and the dose count coincide, so one pen is one four-week cycle and a year of treatment is about 13 pens. On a U-100 insulin syringe, 0.08 mL is the 8-unit mark — a figure that holds only at 250 mcg/mL and is included here for readers comparing the pen with a vial.
Where 20 mcg came from
The dose was set by the fracture trial published by Neer and colleagues in 2001 in the New England Journal of Medicine: 1,637 postmenopausal women with prior vertebral fractures, randomised to 20 mcg, 40 mcg or placebo daily, followed for a median of 21 months.
| Outcome | Placebo | 20 mcg | 40 mcg |
|---|---|---|---|
| New vertebral fracture | 14% | 5% | 4% |
| Relative risk vs placebo | — | 0.35 | 0.31 |
| New non-vertebral fragility fracture | 6% | 3% | 3% |
| Lumbar-spine BMD gain over placebo | — | +9 points | +13 points |
Doubling the dose added bone density but almost nothing in fractures, and 20 mcg is what the label carries. The label's pooled safety table from the two principal trials (1,382 patients, 691 on teriparatide) reports serious adverse events in 16% on teriparatide versus 19% on placebo, and early discontinuation for adverse events in 7% versus 6%; its most common reactions above 10% are joint pain, pain and nausea.
The two-year rule, as it now reads
Teriparatide caused osteosarcoma in rats, and the label's warning keeps that finding. What has changed is the wording around duration. The current label says osteosarcoma "has been reported in patients treated with FORTEO in the post marketing setting; however, an increased risk of osteosarcoma has not been observed in observational studies in humans", that data beyond two years are limited, and that use beyond two years in a lifetime "should only be considered" if fracture risk stays or becomes high again. It also lists who should avoid it because their baseline osteosarcoma risk is higher: people with open growth plates, Paget's disease or other metabolic bone disease, bone metastases or skeletal cancer, prior radiation involving the skeleton, or hereditary conditions that predispose to osteosarcoma.
Why once a day works for a one-hour drug
The label's pharmacokinetics are short: peak about 30 minutes after injection, half-life about 1 hour under the skin, undetectable within 3 hours, bioavailability about 95%. The brief daily spike is the point. The label's mechanism section says teriparatide's skeletal effects "depend upon the pattern of systemic exposure": once-daily dosing preferentially stimulates bone-forming cells, whereas a continuous excess of parathyroid hormone, as in hyperparathyroidism, "may be detrimental to the skeleton". That is also why teriparatide is not a candidate for the weekly or depot formulations common elsewhere on our peptide half-life page.
Six approved versions, one strength
| Product | Holder | Application | First approved |
|---|---|---|---|
| Forteo | Eli Lilly | NDA 021318 | 2002-11-26 |
| Bonsity | Alvogen | NDA 211939 | 2019-10-04 |
| Teriparatide | Teva | ANDA 208569 | 2023-11-16 |
| Teriparatide | Apotex | ANDA 211097 | 2023-11-16 |
| Teriparatide | Almaject | NDA 218771 | 2024-06-04 |
| Teriparatide | Amphastar | ANDA 213641 | 2025-12-12 |
All six are 0.56 mg/2.24 mL pens listed for prescription. A seventh record, Sanofi's Parathar (teriparatide acetate, 200 units per vial), was a diagnostic product and is listed as discontinued. Teriparatide has 4,015 PubMed records, 286 of them tagged as randomised controlled trials, and 182 studies on ClinicalTrials.gov, 6 recruiting (2026-09-28).
What a 10 mg research vial does to the arithmetic
On 2026-09-28 one research-chemical store that publishes its catalogue prices listed "Teriparatide 10mg" at $149.99. The figures that follow are arithmetic on the label's dose, not a description of any product's contents, which are unverified:
| Forteo pen | 10 mg vial | |
|---|---|---|
| Teriparatide | 560 mcg | 10,000 mcg |
| 20 mcg doses | 28 | 500 |
| Equivalent pens | 1 | 17.9 |
| Concentration | 250 mcg/mL | depends on the liquid added |
| Volume of 20 mcg | 0.08 mL | 0.004 mL if mixed in 2 mL |
The last row is the problem. A peptide vial is usually mixed with 1–3 mL of liquid. At 10 mg in 2 mL, the concentration is 5,000 mcg/mL, and a 20 mcg dose is 0.004 mL — 0.4 of one unit mark on a U-100 insulin syringe, below what the syringe can measure. Matching the pen's 250 mcg/mL would take 40 mL, far beyond the vial. A dosing error at this scale is not a few percent; a single unit mark would be 50 mcg, two and a half label doses. How this kind of mismatch arises is covered on our reconstitution guide, and the arithmetic can be checked on Medibact's reconstitution calculator.
Research vials also sit outside the label's other controls: refrigeration from manufacture, a 28-day in-use limit, and a pen that removes measurement from the user. Our page on research-use-only labelling explains what that designation does and does not promise.
What is not known
- The contents of any teriparatide product sold as a research chemical.
- Outcomes at doses other than 20 and 40 mcg daily, or with schedules other than daily, outside trials.
- Long-term osteosarcoma risk beyond about two years, which the label itself calls limited.
The dose for any individual is a prescriber's decision. Teriparatide's row on the peptide dosage chart links back here.
Sources and dates
- FORTEO (teriparatide injection), Eli Lilly and Company, NDA 021318. openFDA drug label, set id aae667c5-381f-4f92-93df-2ed6158d07b0, effective 2026-08-03. Sections 1, 2, 3, 5, 6.1, 12.3, 16. Read 2026-09-28.
- openFDA Drugs@FDA, active ingredient "teriparatide": seven applications and their original approval dates. Read 2026-09-28.
- Neer RM, Arnaud CD, Zanchetta JR, et al. Effect of parathyroid hormone (1-34) on fractures and bone mineral density in postmenopausal women with osteoporosis. N Engl J Med. 2001;344(19):1434-41. PMID 11346808.
- PubMed searches "teriparatide" (4,015) and with randomized controlled trial[pt] (286); ClinicalTrials.gov intervention "teriparatide" (182, 6 recruiting). Run 2026-09-28.
- Public WooCommerce catalogue endpoint of one research-chemical store, searched for "teriparatide", 2026-09-28. List price, not a verified purchase.