Guides
What Is a Low Body Temperature? The Numbers Dr. Wilson Uses
August 3, 2026 · Wilson's T3 Editorial
“Is 97.4 low?” is the question people type into a search box before they type anything about thyroids. The honest answer depends on who is defining low, and Dr. Denis Wilson has defined it precisely for thirty years. This guide collects what he has written about the numbers — the threshold, the typical readings, the method behind the number, and the limits of what one reading can tell you — with links to each source page.
The short answer
From the patient FAQ:
Wilson’s Temperature Syndrome is characterized by body temperatures that average below 98.6 measured orally, typically below 97.8.
Three words in that sentence carry the weight: average, orally, and typically. A single reading of 97.4 is not an average. An underarm or ear reading is not an oral one. And “typically below 97.8” describes most patients, not a line that decides every case.
Why it is an average, not a reading
Body temperature moves through the day, and Dr. Wilson’s method is built around that:
Body temperatures are normally lower in the morning, higher in the afternoon, and lower again in the evening. So if the temperatures are low during the day when they’re supposed to be at their highest, that’s better evidence that there’s a problem.
Temperature patterns are also important and illuminating. How patients feel can be affected not only by how high or low their temperatures are but also on how steady their temps are. This is especially important during T3 therapy. One temperature reading a day is not enough to see how widely the temperature is fluctuating, but more than three a day can be too time consuming.
The arithmetic is deliberately simple:
For each day, add the 3 temperatures together and divide by 3 to get the average.
If your temperature consistently averages below 98.6 then you may be suffering from Wilson’s Temperature Syndrome.
The full method — three oral readings, three hours apart, starting three hours after waking, over several days — is on How to Check Your Body Temperature for WTS, and there is a printable log among the handy tools.
What the readings usually look like
The book gives the range Dr. Wilson actually sees, and it is wider than the single threshold suggests:
Most commonly, the patients that I see who have symptoms of decreased thyroid system function, typically have body temperatures to average around 97.8 degrees. Some patients can be symptomatic with body temperatures of 98.2 degrees, on average. It is rare, but there are a few people who are symptomatic with body temperatures averaging 98.4 whose symptoms resolve when their body temperatures normalize to 98.6 degrees with the WT3 protocol. Again, most Wilson’s Temperature Syndrome patients’ temperatures average around 97.8 degrees, but frequently patients’ temperatures may be found to average from the high 96’s to the mid-97’s. Sometimes there are patients who are found to have body temperatures averaging in the 95’s. I have seen at least one patient with temperatures in the 93’s.
— What Is Wilson’s Temperature Syndrome?, the book
So, in his experience: around 97.8 is the common case; the high 96s to mid 97s are frequent; the 95s happen; and a few people are symptomatic at 98.2 or even 98.4. The number is a pattern, read alongside symptoms — not a pass/fail score.
Why a fraction of a degree could matter
The argument for taking small differences seriously is a biochemical one:
When the body temperature is too low, nearly all of the enzymes in the body function less effectively. This can cause a very wide variety of complaints.
Likewise, a temperature a little above normal (say 100 degrees) is plenty of reason to feel badly and be excused from school or work. Clearly, temperatures that are just as low as 100 degrees is high can easily explain a classic set of symptoms.
That is Dr. Wilson’s position, and it is the part of his work that critics dispute most directly — the objection hub lays out both sides.
What a low reading does not prove
The book is explicit that the number is not a diagnosis on its own:
No, not everyone that has a body temperature that averages below normal has DTSF, Wilson’s Temperature Syndrome, or MED. But a body temperature pattern that averages consistently below normal is more than enough to explain the complaints and symptoms of MED, and Wilson’s Temperature Syndrome should be one of, if not the first, possible causes considered.
In fact, if a patient’s body temperature pattern does not average below normal, then it is far less likely that he will respond favorably to T3 treatment.
— What Is Wilson’s Temperature Syndrome?, the book
Read both halves. A low average is, in his view, reason to consider the syndrome first. A normal average is reason to doubt that T3 therapy would help. The FAQ adds the diagnostic frame: the syndrome is “largely a diagnosis of exclusion” — other explanations are ruled out first — and is “best identified with a therapeutic trial”. That is a conversation to have with a physician, and the Patient Guide to Recruiting a Doctor is written for exactly that conversation.
Before you trust the number, doubt the thermometer
One more thing Dr. Wilson asks readers to do before drawing any conclusion:
By the same token, if your story is consistent with Wilson’s Temperature Syndrome and you find your temperature is normal, by all means, check it with another two or three thermometers! Many patients have found that their thermometers were wrong and their temperatures were low and they have responded well to treatment.
— How to Check Your Body Temperature for WTS
The same page explains which thermometers drift (digital ones after a drop, low batteries or humidity), which stay consistent (liquid-metal and glass alcohol), and why using the same thermometer the same way each time matters more than absolute accuracy.
Where to go from here
- Take the readings properly: How to Check Your Body Temperature for WTS.
- See which of the 53 symptoms Dr. Wilson associates with a low average.
- If the pattern fits, ask for a practitioner who knows the protocol — or bring the guide to your own doctor.
This is a reader’s guide compiled from Dr. Wilson’s published writing; every quotation above is his and links to its source. It is not medical advice, and a body temperature is one observation among many that a physician weighs.