Quick answer
Yes. Essential medicines, including liquids over 100 ml, are allowed in your carry-on. In the UK you need a doctor's letter or prescription for liquids over 100 ml; in the US you declare them to TSA officers at the checkpoint. Medicines with controlled drugs follow separate rules, so check your destination.
Source: GOV.UK: essential medicines, checked 7 Nov 2026
UK airports
Liquid medicines over 100 ml: allowed in hand luggage with a doctor's letter or a copy of your prescription
Tablets or liquids up to 100 ml: no proof needed
Medical equipment: allowed if essential for the journey, such as CPAP and TENS machines; screened separately
Source: GOV.UK, checked 7 Nov 2026
US airports
Liquid medicines: larger amounts allowed in reasonable quantities for your trip
At the checkpoint: declare them to TSA officers for inspection
Source: TSA, checked 7 Nov 2026