Biomagnetism is the study and measurement of the weak magnetic fields naturally produced by nerves and muscles in the body. Every time your heart beats or a neuron fires in your brain, tiny electrical currents generate magnetic fields that can be detected with specialized sensors. These fields are extraordinarily faint, roughly a billion times weaker than a refrigerator magnet, but they carry useful information about how organs are functioning.
The term “biomagnetism” also gets attached to an alternative therapy involving static magnets placed on the body. That practice is fundamentally different from the scientific field, and the two should not be confused. Here’s what the science actually involves, how it’s used in medicine, and where magnet therapy claims stand.
How Your Body Produces Magnetic Fields
Your cells maintain an electrical charge across their membranes. When a nerve sends a signal or a muscle contracts, ions (mainly potassium and sodium) flow through channels in cell membranes, creating small electrical currents. Any electrical current, no matter how small, generates a magnetic field around it. That’s basic physics, and it applies to biology just as it does to a wire carrying electricity.
The heart produces the strongest biomagnetic signal in the body because it’s a large mass of muscle fibers contracting in a coordinated wave. The brain’s magnetic fields are much weaker, on the order of 10 to 100 femtoteslas (a femtotesla is one quadrillionth of a tesla). For context, Earth’s magnetic field is roughly 50 microteslas, which is about a billion times stronger than what your brain puts out. Skeletal muscles also produce measurable magnetic fields, particularly during sustained contraction, driven by gradients of potassium ions along the length of muscle fibers.
Measuring Fields This Small
Detecting biological magnetic fields requires sensors far more sensitive than anything used in everyday electronics. The standard tool for decades has been the SQUID magnetometer (superconducting quantum interference device), which exploits quantum properties of superconducting loops to pick up magnetic flux as small as 1 to 3 femtoteslas. These sensors must be cooled with liquid helium to near absolute zero, making the equipment large and expensive.
A newer competitor is the atomic magnetometer, which uses the quantum behavior of atoms in a vapor to sense magnetic fields. These devices can reach sensitivities of 7 to 10 femtoteslas and don’t require cryogenic cooling, opening the door to smaller, lighter systems. Both types of sensor are shielded from outside interference (like power lines and the Earth’s own field) inside magnetically shielded rooms.
Medical Uses: Brain and Heart Imaging
The two main clinical applications of biomagnetism are magnetoencephalography (MEG) for the brain and magnetocardiography (MCG) for the heart.
MEG for Brain Mapping
MEG records the magnetic fields generated by neuronal currents in the brain. It has two approved clinical uses in the United States: pre-operative brain mapping and localization of seizure sources for epilepsy surgery. Before a surgeon removes brain tissue to treat epilepsy, MEG can pinpoint where seizures originate and identify which nearby areas control movement, sensation, vision, language, and hearing. This helps the surgical team know what can safely be removed.
MEG has a meaningful edge over EEG (the more familiar scalp electrode test) in several ways. Magnetic fields pass through the skull, cerebrospinal fluid, and scalp without distortion, while electrical signals measured by EEG get smeared and weakened by those same tissues. MEG can detect a seizure-related spike from as little as 3 to 4 square centimeters of synchronized brain activity, while EEG needs 6 to 20 square centimeters. MEG also offers better spatial resolution: it can localize a source to within 2 to 3 millimeters, compared to 7 to 10 millimeters for EEG. The tradeoff is that MEG primarily picks up activity oriented sideways to the scalp surface, while EEG can detect activity oriented in any direction.
Research groups are also exploring MEG for early identification of autism in children through differences in how the brain processes sound, for detecting early cognitive decline in Alzheimer’s disease, and for studying psychiatric disorders and head injuries.
MCG for Heart Activity
The magnetocardiogram was the first biomagnetic signal ever measured. Because the heart generates the body’s strongest biological magnetic field, it was the natural starting point for the field in the 1960s. MCG can map the heart’s electrical activity without attaching electrodes to the chest, and like MEG, it avoids the signal distortion caused by body tissues. It remains primarily a research tool, though it shows promise for detecting certain heart rhythm abnormalities and ischemia that standard tests can miss.
FDA-Cleared Electromagnetic Devices
Separate from passive measurement, some medical devices actively deliver pulsed electromagnetic fields (PEMF) to the body. The FDA has cleared several of these, though their approved uses are narrow. All Class III (highest regulatory scrutiny) electromagnetic devices approved by the FDA fall into one category: bone growth stimulation. These are prescribed for fractures that fail to heal on their own, as an add-on treatment after spinal fusion surgery, and for cervical spine fusion in patients at high risk of the bones not joining properly.
Transcranial magnetic stimulation (TMS), which delivers focused magnetic pulses to the brain, has a separate regulatory pathway and is cleared for major depressive disorder and certain other conditions. It works by inducing small electrical currents in targeted brain regions, temporarily altering neural activity.
Do Humans Have a Magnetic Sense?
Many animals, from sea turtles to migratory birds, can sense Earth’s magnetic field and use it for navigation. One leading explanation involves a protein called cryptochrome, found in the eyes, which may undergo light-sensitive chemical reactions that are influenced by magnetic fields. Humans carry a version of this protein, cryptochrome 2 (CRY2), which is heavily expressed in the retina.
In a notable experiment, researchers inserted the gene for human CRY2 into fruit flies whose own magnetosensing system had been disabled. The human protein restored the flies’ ability to sense magnetic fields, and it did so in a light-dependent way, just as animal magnetoreception models predict. This demonstrates that the human version of the protein has the molecular machinery to function as a magnetosensor. Whether humans actually perceive magnetic fields in daily life remains an open question, but the biological hardware appears to be there.
Biomagnetic Pair Therapy: A Different Claim
A practice called Biomagnetic Pair Therapy (BPT), developed by Isaac Goiz Durán, uses the word “biomagnetism” but has no connection to the scientific field described above. In BPT, a practitioner places the north and south poles of static magnets on specific paired locations on the body. The claim is that this normalizes tissue pH, creating conditions where pathogens cannot thrive, and that infections can be eliminated in a matter of days. Practitioners identify which body points to treat using leg-length testing: the practitioner places a magnet on various body areas and observes whether the patient’s right leg appears to shorten.
The evidence for this approach is essentially nonexistent. A systematic review and meta-analysis of randomized trials on static magnets for pain relief, published in the Canadian Medical Association Journal, found no significant difference between magnets and placebo. The average pain reduction was just 2.1 millimeters on a 100-millimeter scale, a difference so small it was statistically indistinguishable from zero. The review concluded that the evidence does not support static magnets for pain relief and that they cannot be recommended as an effective treatment. The broader claims about eliminating infections by correcting pH with magnets have no support from controlled clinical research.
Scientific Biomagnetism vs. Magnet Therapy
The confusion between these two uses of the word “biomagnetism” matters. Scientific biomagnetism is a well-established branch of biophysics with over sixty years of research, specialized instrumentation, and real clinical applications in neurology and cardiology. It involves passively listening to the magnetic fields your body already produces. Magnet therapy, by contrast, involves placing external magnets on the body with the expectation of a healing effect, and the clinical evidence for that effect is not there.
If you’re reading about “biomagnetism” and the context involves SQUID sensors, brain mapping, or cardiac diagnostics, you’re in the realm of established science. If it involves placing magnets on paired body points to treat infections or balance pH, you’re looking at an alternative practice without meaningful clinical support.