Marijuana (weed) typically stays in your blood for a relatively short time compared to other testing methods. Here are the key points about how long weed can be detected in blood:
- Blood tests usually detect THC for up to 12 hours after use in most cases
- Some sources indicate detection in blood can last up to 24 to 48 hours after last use
- In chronic or heavy users, THC may be detectable in blood for several days, with some studies showing detection up to 25 days after last use in very heavy users
- Blood tests detect active THC, which is present only shortly after use, unlike urine tests that detect metabolites which linger longer
In summary, for occasional users, THC is generally detectable in blood for about 12 to 24 hours, but in heavy or chronic users, it can be detected for several days, sometimes up to 25 days. This makes blood tests useful primarily for detecting recent marijuana use rather than long-term use. Other detection windows for comparison:
- Saliva: up to 24-72 hours
- Urine: 3 days to over 30 days depending on frequency of use
- Hair: up to 90 days
Factors affecting detection time include frequency of use, amount consumed, metabolism, body fat, and test sensitivity.
