Objective: To determine whether non-pharmaceutical retail outlets are aboding to the current Medicines and Healthcare products Regulatory Agency (MHRA) national guidelines for over-the-counter (OTC) sales of aspirin and paracetamol. Methods: Stages 1 and 2 of the study deployed eight and four medical students, respectively, to undertake a mystery shopper style investigation. Stage 1: eight medical students attempted to buy ≥96 tablets/capsules aspirin or paracetamol in one transaction in 62 shops. Stage 2: four medical students attempted to purchase 32 paracetamol 500 mg along with a ‘flu remedy preparation also containing paracetamol, in 54 shops. Results: Stage 1 data revealed that 58% and 57% retailers sold more than the MHRA guidelines recommended for paracetamol and aspirin, respectively. We observed that 23% and 28% retailers were willing to sell ≥96 tablets of paracetamol or aspirin with no questions asked. Stage 2 results showed that 57% retailers sold 32×500 mg paracetamol in conjunction with a paracetamol-containing ‘flu preparation; while 98% shops sold 16×paracetamol 500 mg along with a paracetamol-containing ‘flu remedy, with no questions asked of the shopper or advice given. Discussion: MHRA national guidelines for OTC medicines sales appear to be poorly adhered to in non-pharmacy shops. Sales of aspirin and paracetamol OTC must be better regulated in the UK to ultimately reduce morbidity and mortality rates of deliberate and accidental overdoses.