How Long Does THC Stay in Your Hair, Blood and Urine?

Understanding how long Δ9-tetrahydrocannabinol (THC) and its metabolites remain detectable in your body can help with drug testing, medical evaluations or personal awareness. Below, we break down detection windows for hair, blood and urine, highlighting key factors that affect each timeframe.

Key factors influencing detection windows

• Frequency and amount of cannabis use
• Individual metabolism and body fat percentage
• Hydration levels (especially for urine tests)
• Hair color, length and growth rate

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THC in Hair

Hair testing looks for THC metabolites (primarily THC-COOH) that are deposited into the hair shaft via blood. Because hair grows about 1 cm per month, tests typically examine the most recent 3.9 cm (1.5 inches).

Detection window

• Generally 7–90 days after last use
• Some labs may detect up to 120 days in longer hair samples

Why hair testing?

• Harder to cheat compared to urine or blood
• Provides a longer-term “usage history”
• Resistant to short-term fluctuations in hydration or metabolism

Factors affecting hair results

• Hair color and thickness: Darker, coarser hair may bind more drug metabolites
• Cosmetic treatments: Bleaching or dyeing can reduce detectable levels
• Growth rate: Faster or slower hair growth shifts the timeline

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THC in Urine

Urine tests detect 11-nor-9-carboxy-THC (THC-COOH), the main inactive metabolite. Detection windows vary widely based on use patterns.

Typical detection times

• Single or occasional use: 3–5 days
• Moderate use (several times/week): 7–14 days
• Daily/heavy use: 15–30 days
• Very heavy, chronic use: up to 60–90 days

Factors that influence urine tests

• Hydration status: Dilution can lower concentrations (labs check creatinine levels)
• Body fat: THC metabolites are stored in fat cells and released over time
• Exercise: Intense workouts can temporarily raise metabolite levels by mobilizing fat stores
• Lab cut-off values: Common thresholds are 50 ng/mL (initial screen) and 15 ng/mL (confirmatory test)

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THC in Blood

Blood tests measure parent THC rather than its inactive metabolites, making them good for detecting recent use or impairment.

Typical detection times

• Occasional users: up to 1–2 days after last use
• Frequent/heavy users: up to 7 days or more in some cases

Why blood testing?

• Best for assessing recent intoxication (first few hours)
• Used in roadside tests for impairment in many jurisdictions

Factors that influence blood tests

• Time since last use: Levels drop rapidly in first few hours
• Mode of consumption: Smoking/vaping leads to quicker peaks than edibles
• Metabolic rate: Faster metabolism clears THC more quickly

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Putting It All Together

Sample Type	Typical Detection Window	Notes
Hair	7–90 days (sometimes up to 120 days)	Reflects long-term use
Urine	3–90 days (depending on use pattern)	Most common workplace test
Blood	1–2 days (occasional); up to 7+ days (heavy)	Best for recent use/impairment

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Practical Tips

• If you face a drug test, be aware that hair testing offers the longest window of detection, while blood tests focus on recent use.
• Hydration may help dilute urine samples, but labs guard against overly dilute specimens.
• Detox kits or home remedies lack solid scientific backing—time is the only proven way to clear THC metabolites.
• Be honest with medical professionals about cannabis use, especially if you’re having symptoms that concern you. For a free, online symptom check, using the doctor approved Ubie Symptom Checker can help you decide if you need in-person care.

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When to Talk to a Doctor

• If you experience unexpected symptoms—such as extreme anxiety, chest pain or severe dizziness—seek immediate medical attention.
• Always discuss positive or borderline drug test results with a healthcare provider.
• For any life-threatening or serious concerns, do not rely on online information alone—speak to a doctor right away.

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Bottom Line
“How long does THC stay in your hair?” Generally up to 90 days. In urine, it ranges from a few days to several weeks; in blood, from hours to a few days. Your body composition, usage pattern and testing methods all play crucial roles. Stay informed, plan ahead for any required tests, and seek professional guidance when needed.