Prakriti vs. Vikriti: What's the Difference
Prakriti is the proportion of Vata, Pitta, and Kapha fixed at the moment of conception, and it does not change for the rest of life. Vikriti is the proportion present now, the deviation from prakriti that produces symptoms, and it changes with food, season, age, and conduct. A Vata-predominant person in good health has a Vata prakriti and no vikriti; the same person after a month of travel, cold, and irregular meals has a Vata prakriti and a Vata vikriti; the same person after a summer of chilli and late nights has a Vata prakriti and a Pitta vikriti. Treatment is aimed at the vikriti. Prevention is aimed at the prakriti.
What prakriti is
The Charaka Samhita places prakriti among the ten factors examined in every patient. It is set by the doshas predominant in the father's seed and the mother's blood at conception, and shaped by the condition of the womb, the mother's diet and conduct in pregnancy, and the season. Seven types result: the three single types, Vata, Pitta, and Kapha; the three dual types, Vata-Pitta, Pitta-Kapha, and Vata-Kapha; and the rare sama prakriti in which all three are equal. Most people are dual.
Prakriti describes the healthy person. A Pitta prakriti is warm, sharp, hungry, and quick to anger by nature, and none of that is disease. The heat is expected. It becomes vikriti only when it exceeds its own baseline: when the warmth becomes burning, the hunger becomes acidity, and the sharpness becomes rage. The texts describe each prakriti at length so that the physician knows what to expect and does not treat a person's nature as a disorder.
What vikriti is
Vikriti is the present state of the doshas, the tissues, the wastes, and agni, the digestive fire, as read at examination. It is the answer to the question of what has gone out of proportion and where. It is read from the current signs: the tongue, the pulse, the stool, the skin, sleep, appetite, mood, and the complaint the person brings. It is read afresh at every visit, because it moves.
Vikriti is usually an excess of a dosha, since the doshas increase far more readily than they decrease, and it is placed by its stage. The Sushruta Samhita's six stages of disease, the kriyakala, begin with accumulation in the dosha's own seat, the colon for Vata, the small intestine for Pitta, the stomach and chest for Kapha, and proceed through aggravation, overflow into the channels, localisation in a weak tissue, manifestation as a named disease, and complication. Early vikriti is a discomfort in the dosha's seat; late vikriti is a disease with a name.
Why they are often confused
Most people, and most online quizzes, answer questions about the present and call the result prakriti. A Kapha-prakriti person who has been anxious and sleepless for a year will answer as a Vata type. The distinction is made by time. Prakriti questions ask about the lifelong pattern: the build the person has always had, the digestion of childhood and youth, the skin and hair as they have always been, the temperament friends have always known. Vikriti questions ask about the last weeks or months: the current sleep, the current stool, the current mood. When the two answers differ, the difference is the vikriti, and it is the thing to treat.
The other confusion is between vikriti and the ordinary movement of the doshas through the day, the seasons, and the ages of life. Kapha rules the morning, the spring, and childhood; Pitta the midday, the summer and autumn, and the middle years; Vata the late afternoon and night, the cold dry season, and old age. A person feels heavier in spring and drier in old age without being ill. These predictable shifts are why the seasonal routine, ritucharya, exists, and they become vikriti only when they overshoot.
Which one treatment aims at
Shamana, pacification, and shodhana, purification, are aimed at the vikriti. A Pitta vikriti in a Vata-prakriti person is treated with cooling, sweet, and bitter measures, even though the person's nature is cold and dry, because the excess is what is present and what is causing harm. Once the vikriti is resolved, care returns to the prakriti: the Vata person resumes warm, unctuous, regular living to keep Vata from rising again. This is the meaning of the tradition's two aims, to protect the health of the healthy and to remove the disease of the sick. The first is care of prakriti, the second is treatment of vikriti.
There is one exception in reading. A dosha that matches the prakriti is the one most likely to be aggravated, since like increases like, so a Vata person is watched for Vata vikriti above all, and the physician looks there first. Jyotisha, Ayurveda's sister science, reads the same distinction in the chart: the natal placements describe the prakriti, the running dasha describes the season of vikriti.