Tymlos is the brand name of abaloparatide, a 34-amino-acid analogue of parathyroid hormone–related peptide approved in the US in April 2017 for postmenopausal osteoporosis, and in December 2021 to increase bone density in men. It is one of two daily bone-building injections on the US market; the other is teriparatide (Forteo and its generics), whose side effects are on our Forteo side effects page.
This page reports what the trials and the label recorded, with dates. Peptide Lexicon explains the molecule itself in its abaloparatide entry; where Tymlos sits among approved peptide drugs is on our FDA-approved peptides list. Nothing here is a recommendation, and anyone weighing a side effect against treatment should take it to the prescriber.
The numbers by arm: placebo, Tymlos and teriparatide
The pivotal trial, ACTIVE (NCT01343004), randomised 2,463 postmenopausal women to daily injections for 18 months: placebo, abaloparatide 80 mcg, or teriparatide 20 mcg. Placebo and abaloparatide were blinded; teriparatide was given open-label, which means its participants knew what they were taking (Miller 2016, JAMA). The label reports only the Tymlos and placebo columns. The trial's results on ClinicalTrials.gov carry all three, so the table below sets Tymlos beside both.
| Event (posted results, ≥5% threshold) | Placebo (n = 820) | Abaloparatide (n = 822) | Teriparatide, open-label (n = 818) |
|---|---|---|---|
| Palpitations | 3 (0.4%) | 42 (5.1%) | 13 (1.6%) |
| Nausea | 25 (3.0%) | 68 (8.3%) | 42 (5.1%) |
| Dizziness | 50 (6.1%) | 82 (10.0%) | 59 (7.2%) |
| Headache | 49 (6.0%) | 62 (7.5%) | 51 (6.2%) |
| Hypercalciuria (high urine calcium) | 74 (9.0%) | 93 (11.3%) | 102 (12.5%) |
| Hypertension | 52 (6.3%) | 59 (7.2%) | 41 (5.0%) |
| Arthralgia | 80 (9.8%) | 71 (8.6%) | 70 (8.6%) |
| Any serious adverse event | 90 (11.0%) | 80 (9.7%) | 82 (10.0%) |
ClinicalTrials.gov API, NCT01343004 results, read 27 October 2026; percentages are our arithmetic from the posted counts. These are all events recorded, not events the investigators attributed to the drug.
Read across, three things stand out. Palpitations and nausea are the events where abaloparatide separates from both comparators: palpitations about three times the teriparatide rate, nausea about one and a half times. Serious events did not differ between any of the arms. And high urine calcium was more common with teriparatide than with abaloparatide, while the trial's prespecified blood-calcium endpoint went the same way: hypercalcaemia in 3.4% on abaloparatide against 6.4% on teriparatide.
What the label adds
The current label (effective August 2026) carries the trial figures in its own form, and several findings the posted results do not show:
- Injection-site reactions. Assessed daily for the first month, one hour after the dose: redness 58% vs 28% on placebo, swelling 11% vs 3%, pain 10% vs 7%. Severe redness was recorded in 2.9% of Tymlos users.
- Heart rate. A dose-dependent rise developed within 15 minutes of injection and resolved in about six hours. Tachycardia was reported in 2% of women on Tymlos and 1% on placebo; in 5 of the 13 Tymlos cases, symptoms began within an hour of the dose.
- Blood pressure on standing. A drop of at least 20 mmHg systolic or 10 mmHg diastolic one hour after the first injection was measured in 4% on Tymlos and 3% on placebo; at later time points the rates were "generally similar". The label instructs that the first doses be given where the patient can sit or lie down.
- Uric acid. 25% of women on Tymlos with normal baseline uric acid had at least one reading above normal, against 6% on placebo. The label says this was not associated with more gout or joint pain.
- Calcium in the blood. Hypercalcaemia (corrected calcium ≥10.7 mg/dL four hours after a dose) in 3% vs 0.1%; higher in people with mild or moderate kidney impairment (4%) than with normal kidney function (1%).
- Stopping because of side effects. 10% of women on Tymlos stopped for an adverse event, against 6% on placebo — most often for nausea (2%), dizziness, headache or palpitations (1% each).
Men: the ATOM trial
The men's trial randomised 228 men aged 40 to 85 two-to-one to Tymlos or placebo for 12 months (Czerwinski 2022, J Bone Miner Res; NCT03512262). The label's Table 2 lists what occurred more often on Tymlos:
| Event | Tymlos (n = 149) | Placebo (n = 79) |
|---|---|---|
| Injection-site redness | 13% | 5% |
| Dizziness | 9% | 1% |
| Arthralgia | 7% | 1% |
| Injection-site swelling | 7% | 0% |
| Injection-site pain | 6% | 0% |
| Bruising, bloating, diarrhoea, nausea | 3% each | 0% |
The shape differs from the women's trial: local injection reactions lead, and palpitations do not appear in the table. Serious events were 5.4% vs 5.1%. One group is a few hundred men over a year, so the absence of a reaction from a ≥2% table is not evidence that men are spared it.
Serious risks as the label states them
The label's warnings section (August 2026) lists five: hypersensitivity (anaphylaxis, angioedema and hives reported with PTH analogues, added to the warnings in 08/2026), osteosarcoma, orthostatic hypotension, hypercalcaemia, and high urine calcium with kidney stones. Kidney stones were reported in 2.1% of women on Tymlos and 1.7% on placebo. After approval, reports have added vomiting, constipation, fatigue, insomnia, rash and itching, raised blood pressure, leg and back spasms, and injection-site bruising and bleeding; the label notes these come from voluntary reports and their frequency cannot be estimated.
What changed on the label, and when
| Label version (Drugs@FDA) | Date | Osteosarcoma | Duration |
|---|---|---|---|
| Original approval, NDA 208743 | April 2017 | Boxed warning | More than 2 years in a lifetime not recommended |
| Supplement 009 | September 2021 | Boxed warning, unchanged | Unchanged |
| Supplement 010 (men's indication added) | December 2021 | "Osteosarcoma Boxed Warning, Removed"; warning moved to section 5 | Unchanged |
| Supplement 018 (current) | August 2026 | Warning section only | Unchanged |
Read from the label PDFs on Drugs@FDA, 27 October 2026. The rat finding behind the warning is unchanged: in a two-year study, osteosarcoma reached 87% of high-dose males and 62% of high-dose females, at exposures 4 to 28 times the human dose, against 0–2% of untreated rats. The label says it is unknown whether this applies to humans, and that observational studies of PTH-analog users have not shown an increased risk.
The comparison with Forteo is instructive. Forteo lost its boxed warning thirteen months earlier, in November 2020, and at the same time its two-year limit was softened to "should only be considered if a patient remains at or has returned to having a high risk for fracture". Tymlos's label still says use beyond two years "is not recommended" — the two drugs in the same class now carry different duration wording. The detail of Forteo's change is on the teriparatide dosage page.
What is not established
- Osteosarcoma risk in humans beyond two years, which the label calls limited.
- How long each common side effect lasts in an individual: the trials reported incidence, not duration, except for the heart-rate rise and the first-hour blood pressure drop.
- A blinded comparison with teriparatide: the only head-to-head data come from an open-label arm.
- Side effects outside the trial populations, such as people under 49 or with significant kidney disease, who were few or excluded.
Questions about whether a reaction is expected or a reason to stop belong with the prescriber or pharmacist; reactions can be reported to FDA's MedWatch. How injection-site reactions compare across peptide drugs is on our injection-site reactions page.
Sources and dates
- Tymlos (abaloparatide) prescribing information, label effective August 2026, via openFDA drug label API — read 27 October 2026.
- Drugs@FDA, NDA 208743: label PDFs for the original approval (2017), supplements 009 (09/2021), 010 (12/2021) and 018 (08/2026) — read 27 October 2026.
- ClinicalTrials.gov API v2, NCT01343004 (ACTIVE), posted adverse events — read 27 October 2026.
- Miller PD et al. Effect of abaloparatide vs placebo on new vertebral fractures in postmenopausal women with osteoporosis. JAMA. 2016;316(7):722–33. PMID 27533157.
- Czerwinski E et al. The efficacy and safety of abaloparatide-SC in men with osteoporosis. J Bone Miner Res. 2022;37(12):2435–42. PMID 36190391.