Unsealed tracers

Feasibility review

Tritium (H-3) for research

A low-energy beta label that leaves a molecule almost unchanged, for binding, cell and metabolism studies.

Half-life: 12.32 years
Beta max: 18.59 keV
Decay: Beta minus to He-3
Exempt quantity: 1,000 µCi

Request an H-3 feasibility review How ordering works

H-3 at a glanceIAEA evaluated data

a Energy of the emitted beta particles, calculated from the IAEA endpoint energy; dashed line: mean energy. b Activity left after the reference date. Data: IAEA [1]

Research applications

Where H-3 does the work.

Figures are simulated examples of each measurement.

Pharmacology
Receptor binding^{2, 3, 4}
Tritiated ligands measure how many receptors a tissue has and how tightly a ligand binds them.
More: Receptor binding
Specific binding is total binding minus nonspecific binding, measured with excess unlabeled ligand. In rat brain, a tritiated muscarinic antagonist bound with a dissociation constant of 60 pM, at 65 pmol per gram of brain.
The same ligands map receptors in tissue sections by autoradiography, nucleus by nucleus in the brainstem.
Tritium leaves a ligand almost unchanged. Each tritium atom adds about 28.8 Ci/mmol, and radioligands usually carry two to four, for 50 to 100 Ci/mmol.
Drug discovery
Scintillation proximity assays^{4, 5, 6}
Binding is read in the well, with no step to separate bound from free ligand.
More: Scintillation proximity assays
The receptor sits on a bead that contains scintillant. Tritium betas travel less than 8 µm in water, so only bound ligand is close enough to make the bead give light.
Reading the same wells every 30 seconds follows binding and dissociation as they happen.
Cell biology
DNA synthesis and cell division^{7, 8}
[³H]thymidine marks cells that are copying their DNA.
More: DNA synthesis and cell division
In quiescent mouse fibroblasts given serum growth factors, DNA synthesis began 12 to 14 hours later, and the whole population had entered S phase by 24 hours.
In 1957, autoradiographs of chromosomes labeled with [³H]thymidine showed how they duplicate. Tritium betas travel little more than a micron in photographic emulsion, which gives fine detail.
Metabolism
Glucose uptake^{9, 10, 11}
A short pulse of 2-deoxy-D-[³H]glucose measures glucose transport into cells.
More: Glucose uptake
A 10 minute pulse reads the transport rate, and cytochalasin B defines the background.
Insulin raised deoxyglucose uptake 6- to 14-fold in differentiated 3T3-L1 fat cells, with half of the maximum at 550 pM insulin.
Drug metabolism
Metabolite profiling^{4, 12}
A tritium-labeled drug candidate lets researchers find and measure its metabolites by their radioactivity.
More: Metabolite profiling
Counting radioactivity measures every drug-related peak, without relying on each metabolite's structure or mass spectrometry response.
Tritium costs less to introduce than carbon-14 and is preferred for early in vitro work. The label must sit where metabolism will not remove it.
Radioactivity counting
Liquid scintillation counting^{13, 14}
Unquenched tritium counts at about 65 percent efficiency, and quench lowers it further.
More: Liquid scintillation counting
Quench cuts the light each beta makes. Tritium's low energy makes it very sensitive to quench, so labs correct each sample with a quench curve built from quenched standards.
Carbon-14 counts at about 94 percent unquenched.

Forms

H-3 forms researchers ask for

Every form is confirmed with its manufacturer before you order.

Labeled compound
A ligand, nucleoside, sugar or drug candidate labeled with tritium, in solution
Binding, cell and metabolism studies
Feasibility review
Custom labeling
Tritium labeling of a compound you supply or specify
New ligands and drug candidates
Feasibility review
Counting standard
Sealed tritium standard in a scintillation vial
Counter efficiency and quench checks
Feasibility review

Activity, certificate and lead time are set with the manufacturer at quote.

Before you order

Plan for decay and licensing.

Plan around decay

H-3 has a half-life of 12.32 years and loses about 0.1 percent of its activity each week. Ask for the activity you need on the day you start using it.

Activity remaining after

1 year94.5%
5 years75.5%
10 years57%
20 years32.5%

Licensing

Exempt quantityNeeds a license1 mCi

Activity of one vial, log scale

A single quantity of H-3 at or below 1,000 µCi is an exempt quantity under 10 CFR 30.71, Schedule B. Above that, your institution needs a license that covers it.

Combining exempt quantities to exceed the limit is not covered.
Tritium betas travel about 6 mm in air and do not pass the outer layer of skin. The hazard is intake, and many tritiated compounds pass through gloves and skin.
Survey meters cannot detect laboratory amounts of tritium; liquid scintillation counting is the readily available way to find it.
Agreement States apply equivalent rules. Your RSO reviews the exact material before you order.

Sources: 15, 16, 17

Start a request

Request a feasibility review for H-3.

No license file needed to ask. A scientist reads every request and replies with the next step.

Name the compoundGive the molecule, the labeled position if it matters and the specific activity you need.
Plan the countingConfirm the cocktail, counter and quench standards for your samples.
Ask your RSO earlyThey set the limits, storage, wipe tests and waste route for tritium.

Decay data

H-3 decay data

Decay schemeH-3 to He-3

Energies in keV, with emission probability per decay. Levels not to scale. Data: IAEA [1]

Half-life: 12.32 years ± 0.02
Decay mode: Beta minus (100%)
Daughter: He-3
Decay energy (Q): 18.592 keV

H-3 emissions
Radiation	Energy (keV)	Per 100 decays
Beta	18.6 max, 5.7 mean	100

Source: IAEA LiveChart of Nuclides, ENSDF evaluation by J.E. Purcell and C.G. Sheu (literature cutoff 30 June 2015), retrieved 25 September 2026 [1]. Reference values; a manufacturer's certificate states the activity of a specific lot.

Questions, answered

H-3 questions

How long does tritium last?

Its activity halves every 12.32 years, so it loses about 5.5 percent a year. Most experiments need no decay correction.

Can we buy tritium without a radioactive materials license?

For small amounts, possibly. A single quantity of H-3 at or below 1,000 microcuries (1 mCi) is an exempt quantity under 10 CFR 30.71, and a distributor licensed under 10 CFR 32.18 can supply exempt quantities to users without a license. Larger amounts need a license that covers them. Your RSO decides how your institution handles each case.

Why can a survey meter not find tritium?

Its betas are too weak: they travel about 6 mm in air. Labs find tritium by liquid scintillation counting, including wipe samples from work surfaces.

What specific activity can tritium give?

About 28.8 Ci/mmol for each tritium atom, roughly 500 times a single carbon-14 label. Radioligands usually carry two to four tritium atoms, for 50 to 100 Ci/mmol.

Should we label with tritium or carbon-14?

Tritium gives higher specific activity and costs less to introduce, so it suits early in vitro work. Carbon-14 is less likely to be lost in metabolism and is usual for later in vivo studies.

What should we tell you about the compound?

The molecule, the labeled position if it matters, the specific activity and the amount. We confirm a matching product and certificate with the manufacturer before you order.

More isotopes

Carbon-14 for research
C-14 · Half-life 5,700 years
The label that sits in a molecule's carbon backbone, for following carbon through cells, animals, plants and soil.
Phosphorus-32 for research
P-32 · Half-life 14.27 days
An energetic beta label for DNA and RNA probes, kinase assays and gel shift experiments.
Iodine-125 for research
I-125 · Half-life 59.41 days
A high specific activity label for proteins, peptides and receptor ligands, counted in a gamma counter.
Sulfur-35 for research
S-35 · Half-life 87.37 days
The label for newly made proteins, G protein activation and sharp autoradiographs.
Americium-241 for research
Am-241 · Half-life 432.6 years
Alpha particles near 5.49 MeV and a 59.5 keV gamma ray, from one long-lived source.
Barium-133 for research
Ba-133 · Half-life 10.55 years
Gamma lines from 81 to 384 keV and cesium X-rays near 31 keV: a standard for low- and mid-energy calibration.

Sources

References

IAEA Nuclear Data Section. LiveChart of Nuclides, H-3 decay data (ENSDF evaluation). Retrieved 25 September 2026. www-nds.iaea.org/relnsd/vcharthtml/VChartHTML.html
Yamamura HI, Snyder SH. Muscarinic cholinergic binding in rat brain. Proc Natl Acad Sci U S A. 1974;71(5):1725-1729. doi.org/10.1073/pnas.71.5.1725
Wamsley JK, Lewis MS, Young WS 3rd, Kuhar MJ. Autoradiographic localization of muscarinic cholinergic receptors in rat brainstem. J Neurosci. 1981;1(2):176-191. doi.org/10.1523/JNEUROSCI.01-02-00176.1981
Atzrodt J, Derdau V, Kerr WJ, Reid M. Deuterium- and tritium-labelled compounds: applications in the life sciences. Angew Chem Int Ed Engl. 2018;57(7):1758-1784. doi.org/10.1002/anie.201704146
Udenfriend S, Gerber L, Nelson N. Scintillation proximity assay: a sensitive and continuous isotopic method for monitoring ligand/receptor and antigen/antibody interactions. Anal Biochem. 1987;161(2):494-500. doi.org/10.1016/0003-2697(87)90479-9
Xia L, de Vries H, IJzerman AP, Heitman LH. Scintillation proximity assay (SPA) as a new approach to determine a ligand's kinetic profile. A case in point for the adenosine A1 receptor. Purinergic Signal. 2016;12(1):115-126. doi.org/10.1007/s11302-015-9485-0
Pledger WJ, Stiles CD, Antoniades HN, Scher CD. Induction of DNA synthesis in BALB/c 3T3 cells by serum components: reevaluation of the commitment process. Proc Natl Acad Sci U S A. 1977;74(10):4481-4485. doi.org/10.1073/pnas.74.10.4481
Taylor JH, Woods PS, Hughes WL. The organization and duplication of chromosomes as revealed by autoradiographic studies using tritium-labeled thymidine. Proc Natl Acad Sci U S A. 1957;43(1):122-128. doi.org/10.1073/pnas.43.1.122
Park CH, Chang JS. Protocol for measuring in vivo, ex vivo, and in vitro glucose uptake in brown adipocytes. STAR Protoc. 2025;6(4):104244. doi.org/10.1016/j.xpro.2025.104244
Resh MD. Development of insulin responsiveness of the glucose transporter and the (Na+,K+)-adenosine triphosphatase during in vitro adipocyte differentiation. J Biol Chem. 1982;257(12):6978-6986. doi.org/10.1016/S0021-9258(18)34526-5
Harrison SA, Buxton JM, Clancy BM, Czech MP. Insulin regulation of hexose transport in mouse 3T3-L1 cells expressing the human HepG2 glucose transporter. J Biol Chem. 1990;265(33):20106-20116. doi.org/10.1016/S0021-9258(17)30476-3
Isin EM, Elmore CS, Nilsson GN, Thompson RA, Weidolf L. Use of radiolabeled compounds in drug metabolism and pharmacokinetic studies. Chem Res Toxicol. 2012;25(3):532-542. doi.org/10.1021/tx2005212
US Environmental Protection Agency, Nuclear Regulatory Commission and other federal agencies. Multi-Agency Radiological Laboratory Analytical Protocols Manual (MARLAP), Volume II, Chapter 15: Quantification of radionuclides. NUREG-1576, EPA 402-B-04-001B; 2004. www.epa.gov/sites/default/files/2015-05/documents/402-b-04-001b-15-final.pdf
Zimmerman BE, Collé R. Standardization of 63Ni by 4πβ liquid scintillation spectrometry with 3H-standard efficiency tracing. J Res Natl Inst Stand Technol. 1997;102(4):455-477. doi.org/10.6028/jres.102.031
U.S. Nuclear Regulatory Commission. 10 CFR 30.71, Schedule B (exempt quantities). eCFR, current as of 23 September 2026. www.ecfr.gov/current/title-10/section-30.71
U.S. Nuclear Regulatory Commission. 10 CFR 30.18, Exempt quantities. eCFR, current as of 23 September 2026. www.ecfr.gov/current/title-10/section-30.18
Emory University Environmental Health and Safety Office. Nuclide safety data sheet: hydrogen-3 (tritium). ehso.emory.edu/sso/documents/content-guidelines/nuclide-data-safety-sheets.pdf

Technical review by ConductScience, 25 September 2026. Next review 25 September 2027.

Need H-3 for a specific instrument or measurement?

Start with what you know. Your RSO and supplier documents come after review. See all radioactive isotopes.

Start a request

Tritium (H-3) for research

Receptor binding2, 3, 4

Scintillation proximity assays4, 5, 6

DNA synthesis and cell division7, 8

Glucose uptake9, 10, 11

Metabolite profiling4, 12

Liquid scintillation counting13, 14

Labeled compound

Custom labeling

Counting standard

Plan around decay

Licensing

Carbon-14 for research

Phosphorus-32 for research

Iodine-125 for research

Sulfur-35 for research

Americium-241 for research

Barium-133 for research

Need H-3 for a specific instrument or measurement?

Receptor binding^{2, 3, 4}

Scintillation proximity assays^{4, 5, 6}

DNA synthesis and cell division^{7, 8}

Glucose uptake^{9, 10, 11}

Metabolite profiling^{4, 12}

Liquid scintillation counting^{13, 14}