King George III’s illness is now thought to have been a serious mental health condition, most likely a form of bipolar disorder with episodes of mania and psychosis, rather than a purely physical disease like porphyria.

Quick Scoop: What was King George’s illness?

Most historians today think:

  • He suffered from a long‑term mental illness, with clear manic episodes (pressured, nonstop talking, racing thoughts, little sleep) and periods of relative stability.
  • Older theories said he had porphyria, a rare genetic blood disorder causing pain, insomnia, and mental changes, but recent research has largely moved away from this explanation.
  • Linguistic analysis of his letters shows his sentences became extremely long, repetitive, and disorganized during illness periods, which fits a manic or psychotic picture better than porphyria.

In short: we cannot be 100% sure, but the best‑supported modern view is that King George III had a severe psychiatric illness—probably bipolar disorder with psychotic features—rather than primarily a blood disorder.

What symptoms did he show?

Contemporaries described symptoms that went far beyond “eccentric” behavior:

  • Intense episodes of talking rapidly and at great length, with sentences running on for hundreds of words.
  • Insomnia and extreme restlessness, sometimes pacing and talking through the night.
  • Confused, disorganized thinking and “madness” as observers called it, including loss of normal judgment.
  • Periods of apparent recovery between episodes, suggesting a relapsing‑remitting course rather than a single, continuous decline.

These episodes became so severe that his son ruled as Prince Regent from 1811, because George III was declared unfit to govern.

Why did people think it was porphyria?

For decades in the 20th century, the “porphyria theory” was extremely popular:

  • Two psychiatrists in the 1960s argued that his symptoms matched acute intermittent porphyria, a genetic disorder affecting the nervous system and causing abdominal pain, discolored urine, and mental changes.
  • The theory appealed to people because it “medicalized” his madness as a blood disorder rather than a mental illness, which was heavily stigmatized.

However, later historians and medical researchers scrutinized the records and found:

  • Many key porphyria signs (like characteristic abdominal crises and certain lab findings) were not clearly documented.
  • His symptom pattern matched recurrent mood episodes and psychosis more closely than acute toxic attacks.

So porphyria is now generally seen as unlikely , though you’ll still see it mentioned in older books and popular media.

Modern interpretation: likely bipolar disorder

Recent work, including computational analysis of his letters, strongly points toward a mood disorder:

  • Researchers measured changes in his writing—sentence length, repetition, and complexity—and found striking shifts during illness periods that resemble modern manic language.
  • His combination of insomnia, pressured speech, and disorganized thought fits many modern descriptions of severe mania with psychotic features.

Because records are incomplete and diagnosis is happening centuries later, historians stay cautious:

  • You’ll often see phrasing like “most consistent with bipolar disorder” rather than a firm diagnosis.
  • Some also suggest overlapping possibilities, like a neurodegenerative process late in life, on top of his long‑standing psychiatric illness.

But overall, bipolar‑type illness is now the leading explanation.

How people talk about it today (forums & shows)

Because of series like “Queen Charlotte: A Bridgerton Story,” there’s a fresh wave of online discussion:

  • Viewers often ask “what was King George’s illness?” and debate whether the show is depicting schizophrenia, bipolar disorder, or something else.
  • Many commenters point out that the historical record is limited and biased; much of his private behavior was hidden, and doctors didn’t use modern diagnostic terms.
  • Historically minded fans usually echo historians: we can’t know with absolute certainty, but bipolar disorder with psychosis fits the evidence better than schizophrenia or pure porphyria.

In forum discussions, the consensus tends to be: “No one knows for sure, but modern medicine would probably call it a severe mood disorder rather than just ‘madness’ or a blood disease.”

TL;DR:
When people ask “what was King George’s illness,” the current best answer is: a severe mental illness, most likely a bipolar‑type disorder with manic and psychotic episodes, not conclusively proven but strongly supported by his symptoms and by modern analyses of his letters.

Information gathered from public forums or data available on the internet and portrayed here.