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Short answer: Interferential current therapy (IFC) is a form of transcutaneous electrical stimulation for pain relief that crosses two medium-frequency alternating currents so that they interfere and produce a low-frequency amplitude modulation. In the United States, IFC devices are regulated by the FDA as Class II devices under 21 CFR 882.5890, product code LIH. This page is general product and regulatory information, not medical advice.
What is interferential current therapy?
A 2018 systematic review and meta-analysis in the Brazilian Journal of Physical Therapy describes interferential current as medium-frequency alternating currents that cross and interfere with each other, producing an amplitude-modulated frequency in the 1-200 Hz range. In the six studies of that review that reported a carrier frequency, it was set at 4000 Hz. The same paper describes conventional TENS (transcutaneous electrical nerve stimulation) as pulsed currents, typically 1-200 Hz with a pulse duration of 100-200 microseconds.
The scope of this page is the device and its regulatory identity, for laboratory, clinic and supply staff who need to recognise what an interferential unit is. It does not give treatment parameters, dosing or electrode-placement instructions, and it does not recommend a treatment for any person.
Interferential current vs TENS
The two are often confused because the FDA files both under the same regulation. The table below sets out what the cited sources state.
| Point | Interferential current (IFC) | Conventional TENS | Source |
|---|---|---|---|
| Current type | Medium-frequency alternating currents that cross and interfere | Pulsed currents | Almeida et al. 2018 |
| Effective frequency | Amplitude-modulated frequency of 1-200 Hz | Typically 1-200 Hz | Almeida et al. 2018 |
| Carrier frequency | Set at 4000 Hz in six studies in the review | Not applicable | Almeida et al. 2018 |
| Pulse duration | Not stated in the source | Typically 100-200 microseconds | Almeida et al. 2018 |
| FDA regulation | 21 CFR 882.5890, Class II, product code LIH | Same regulation, “Transcutaneous electrical nerve stimulator for pain relief” | FDA Product Classification |
On pain outcomes, the same meta-analysis (8 studies, 825 patients) concluded that TENS and interferential current have similar effects. Its authors also reported high heterogeneity (I2 of 91% for pooled visual analogue scale results), moderate study quality and variation in the parameters used, and called for new trials. A claim that IFC is superior to TENS is therefore not established by that meta-analysis.
How the FDA classifies interferential current devices
The FDA Product Classification database lists a device named “interferential current therapy” under product code LIH. The entry gives the regulation description “Transcutaneous electrical nerve stimulator for pain relief”, regulation number 21 CFR 882.5890, device class 2, review panel Neurology, and submission type 510(k). It is not an implanted device and is not listed as life-sustaining. The entry is marked as not exempt from good manufacturing practice requirements. The database page shows an update date of 10/26/2026.
21 CFR 882.5890 is classified as Class II (performance standards). The submission type shown in the database is 510(k) (compare the FDA De Novo classification route). The FDA is described in more general terms in the FDA (Food and Drug Administration) entry, and the statutory background for device classes is in the Medical Device Amendments of 1976 entry.
As a real example of the product code in use, the FDA 510(k) database lists K202725, the ETD4000 from Therasigma LLC, with a decision date of 03/26/2021, a decision of Substantially Equivalent, product code LIH, regulation 882.5890 and classification name “Interferential Current Therapy”. The record is cited here only to show how a cleared unit appears in the database; it is not an endorsement of the device.
Recognized consensus standard
The LIH classification entry lists IEC 60601-2-10 (nerve and muscle stimulators, basic safety and essential performance), Edition 2.2 of 2023-01, as an FDA-recognized consensus standard. The entry shows the device as eligible for 510(k) Third Party Review. For how recognition works in general, see FDA Recognized Consensus Standards.
What to check when evaluating an interferential unit
This checklist uses only items that can be looked up in public regulator records. It is a record-checking aid, not a purchasing recommendation, and it makes no claim about price, availability or which unit is best.
- Product code and regulation. Confirm the unit is listed under product code LIH and 21 CFR 882.5890 in the FDA Product Classification database.
- 510(k) number. Ask the manufacturer for the 510(k) number and confirm the decision (Substantially Equivalent) in the FDA 510(k) database, as in the K202725 example above.
- Standard. Note whether the manufacturer’s documentation refers to IEC 60601-2-10, the FDA-recognized standard for this device type.
- Manufacturer instructions for use. The intended use, contraindications and operating instructions come from the manufacturer’s labelling for that specific unit, not from a general web page.
- Consumables. Electrodes and gel used with stimulation devices appear on supply lists; for a sample office list see the chiropractic office supply checklist.
Common misunderstandings
- “IFC is a separate regulatory category from TENS.” In the FDA database, the interferential current therapy device is filed under the TENS regulation, 21 CFR 882.5890.
- “IFC reaches deeper tissue than TENS.” This is a common marketing claim. It is not established by the FDA records or the 2018 meta-analysis cited here, which found similar pain outcomes for the two.
- “A product code means a specific unit is proven effective.” A 510(k) clearance with the decision Substantially Equivalent is a determination about equivalence to a predicate device under the classification, not a finding about outcomes for an individual.
- “The frequency on the display is the carrier frequency.” The source describes a carrier set at 4000 Hz in six studies and an amplitude-modulated effective frequency of 1-200 Hz; these are different quantities.
FAQ
What is interferential current therapy?
It is transcutaneous electrical stimulation for pain relief that uses two medium-frequency alternating currents which cross and interfere, producing an amplitude-modulated frequency of 1-200 Hz (Almeida et al. 2018).
What is the difference between interferential current and TENS?
TENS uses pulsed currents, typically 1-200 Hz with 100-200 microsecond pulses. IFC uses crossed medium-frequency alternating currents, with a carrier of 4000 Hz in the six studies that reported one. A meta-analysis of 8 studies and 825 patients found similar pain outcomes, with heterogeneity and moderate study quality noted by the authors.
How is an interferential current device regulated in the US?
It is a Class 2 device under 21 CFR 882.5890, product code LIH, cleared by 510(k), with IEC 60601-2-10 listed by the FDA as a recognized consensus standard.
Can this page tell me whether interferential therapy is right for me?
No. This is general product and regulatory information. Questions about treatment belong with a licensed clinician.
Sources
- U.S. Food and Drug Administration, Product Classification, product code LIH (interferential current therapy): accessdata.fda.gov, classification LIH. Checked 31 October 2026.
- 21 CFR 882.5890, Transcutaneous electrical nerve stimulator for pain relief: eCFR. Checked 31 October 2026.
- FDA 510(k) database record K202725: accessdata.fda.gov, K202725. Checked 31 October 2026.
- Almeida CC et al. Brazilian Journal of Physical Therapy 2018;22(5):347-354, a systematic review and meta-analysis of TENS and interferential current for pain: PMC6157468. Checked 31 October 2026.
