Carry on baggage
Yes (<350ml)
Checked baggage
Yes
Certain powder and granular materials inside weighted blankets (e.g., glass beads, poly-pellets, sand, or pebbles) are limited to a quantity of 350 mL or less (roughly the size of a soda can). There are no exceptions for medical reasons.
Note that if the weighted blanket contains over 350mL of such powder or granular materials, it is not permitted in the carry-on baggage.