What is THC? THC is short for delta-9-tetrahydrocannabinol, the compound behind the high cannabis is known for. It's one of more than 100 cannabinoids the plant makes, and it's usually the first number shoppers look for on a label. This guide covers THC's main forms, how it works in your body and what research supports. It also compares THC with CBD and explains detection times and where THC stands under Michigan and federal law.
What is THC?
THC is a plant cannabinoid, one of the natural compounds cannabis makes in the tiny resin glands on its flowers. It's intoxicating, which means it changes perception, mood and thinking for a while after you use it.
Living plants make very little THC directly. They make THCA, an acid form that turns into THC when it's heated by a flame, a vaporizer or an oven. Some of that change also happens slowly as flower ages or sits in light. That's why raw flower labels often list THCA, and why cooking with cannabis starts with a heating step called decarboxylation. Our THC vs. THCA guide goes deeper.
One common mix-up: THC isn't an endocannabinoid. Your body makes its own cannabinoids, and THC happens to act on the same receptors they use. That overlap is where its effects come from.
Main forms: THCA, delta-9, delta-8, delta-10 and THCV
| Form | What it is | Intoxicating? |
|---|---|---|
| THCA | The acid form in raw flower; heat turns it into delta-9 THC | Not until it's heated |
| Delta-9 THC | The main form behind cannabis's effects | Yes |
| Delta-8 THC | A close variant with one chemical bond in a different spot, often made from CBD | Yes; early research suggests it's less potent |
| Delta-10 THC | Made in a lab from hemp CBD; it doesn't occur naturally in meaningful amounts | Reported to be, but little studied |
| THCV | A cousin with a shorter side chain, present in small amounts in some plants | Not at the low doses studied so far |
When people say THC, they almost always mean delta-9. Our guide to the different types of THC covers each form in more detail.
How does THC work? CB1, CB2 and the endocannabinoid system
Your endocannabinoid system is a signaling network with three parts: cannabinoids your body produces, receptors for them, and enzymes that build and clear them. THC fits into two of those receptors.
- CB1 receptors sit mainly on nerve endings in the brain and spinal cord. They're plentiful in areas tied to memory, emotion, thinking and coordination, and THC's action there produces the high.
- CB2 receptors are found mostly on immune cells and on support cells in the brain.
THC switches these receptors on only partway, so scientists call it a partial agonist. Anandamide, one of the body's own cannabinoids, works the same way, while another, called 2-AG, switches them on fully. Our plain-English guide to the endocannabinoid system explains the rest.
What research supports, and where it falls short
Some THC findings are well established. Many popular claims are not.
- Approved medicines. Dronabinol, a synthetic version of THC, has FDA approval for nausea from cancer chemotherapy and for poor appetite linked to weight loss in AIDS. Nabilone, a synthetic compound with a structure close to THC's, is approved for chemotherapy nausea. Cannabis itself has no FDA approval for any disease or condition.
- Pain. A 2017 report from the National Academies of Sciences, Engineering, and Medicine found conclusive or substantial evidence that cannabis is effective for chronic pain in adults. It reached the same level of evidence for oral cannabinoids against chemotherapy nausea and for muscle stiffness symptoms reported by people with multiple sclerosis.
- Sleep. The same report found only moderate evidence for short-term sleep improvements, and mostly from one cannabis-based medicine. The people studied had sleep disrupted by sleep apnea, fibromyalgia, chronic pain or multiple sclerosis. That's a narrow finding, not proof that THC fixes insomnia.
These conclusions come from studies of specific products, doses and patients, and a dispensary product isn't the same thing. If you have a health condition, talk with a clinician before using cannabis for it.
Short-term THC effects and risks
THC effects depend on the dose, the person and how it's taken. The National Institute on Drug Abuse lists short-term effects that can include:
- an altered sense of time
- impaired thinking, memory and body movement
- feeling irritable or restless
- a faster heart rate
- anxiety, fear, distrust or panic, and sometimes hallucinations, especially after taking a lot
Driving is the biggest everyday risk. The National Academies found substantial evidence linking cannabis use to a higher risk of motor vehicle crashes. It also found substantial evidence of a link with developing schizophrenia or other psychoses, with the highest risk among the most frequent users. NIDA adds that daily or near-daily use is associated with cannabis use disorder.
Cannabis can interact with other medicines, and NIDA notes that use during pregnancy may harm a baby's health after birth. Talk with your doctor if you're pregnant, breastfeeding, take medications or live with a heart or mental health condition. 21+ only. Please consume responsibly.
THC vs CBD
These two cannabinoids get the most attention, and they behave very differently.
| THC | CBD | |
|---|---|---|
| Intoxicating? | Yes | Not like THC |
| Usual source | THC-rich cannabis | Hemp or CBD-rich cannabis |
| Possible side effects | Impaired memory and coordination, faster heart rate, anxiety at high doses | Drowsiness, decreased appetite, vomiting, diarrhea |
Like other cannabinoid products, CBD can interact with other drugs, so mention it to your doctor or pharmacist. Our side-by-side CBD vs. THC comparison covers products and ratios.
Product forms
THC comes in many formats, and the format changes how fast and how long you feel it:
- Inhaled: flower, pre-rolls, vapes and concentrates act within minutes.
- Swallowed: edibles, drinks and capsules take longer to kick in. NIDA warns that people may take more while they wait, which raises the risk of serious negative effects.
- Under the tongue: tinctures can be held in the mouth or swallowed.
- On skin: topicals are applied to the skin.
Whatever the format, check the THC per serving and per package, and start low if a product is new to you.
Is THC legal in Michigan? State and federal law
Yes, for adults. Under Michigan's 2018 voter-approved law, adults 21 and older may buy, possess and use marijuana, and licensed stores sell THC products to them. Registered medical patients 18 and older with a valid card can buy as well.
- Delta-8 THC: Michigan regulates it as marijuana. Since October 11, 2021, only businesses licensed by the Cannabis Regulatory Agency may sell it, and licensed products may contain no more than 10% delta-8.
- Federal law: as of October 2026, a federal rescheduling action has moved marijuana medicines approved by the FDA, and marijuana covered by a state medical license, to Schedule III. All other marijuana, including adult-use, remains Schedule I.
- Hemp-derived THC: a federal change to the definition of hemp is set to take effect in late 2026, as of October 2026, and further changes are possible. It would end legal-hemp status for most intoxicating hemp-THC products.
Michigan's law stops at the state line, so don't travel across state lines with cannabis. Our Michigan cannabis law guide covers limits and where you can use it.
How long THC stays detectable
Most drug screens hunt for THC-COOH, a breakdown product with no effects of its own. THC tucks itself into fat tissue and seeps back out slowly, so frequent users can test positive long after the high is gone.
A 2012 clinical guide from the federal Substance Abuse and Mental Health Services Administration gives these rough urine windows:
| Use pattern | Approximate urine detection window |
|---|---|
| Single use | Up to 3 days |
| Moderate use | Up to 4 days |
| Heavy use | Up to 10 days |
| Chronic, heavy use | 30 to 36 days |
These are estimates, not promises. Your THC detection window depends on body fat, metabolism, hydration, product strength and the lab's cutoff. Michigan employers may also still enforce drug policies, even though adult use is legal. Blood, saliva and hair tests each have their own windows, so ask what kind of test you face.
