Her first international successes were medals at Junior World and European championships. Merkushyna is a two-time bronze medalist in girls' individual at the 2013 and 2016 Junior Worlds, a two-time silver medalist in relay, a three-time Junior European champion, and a three-time European medalist. In 2012 she qualified for 2012 Winter Youth Olympics in Innsbruck, Austria, where she was 14th both in sprint and pursuit.
Before receiving a spot in the Ukrainian national team, she participated in IBU Cup competitions. Her first World Cup race was in Swedish Östersund in 2014–15 season, where she finished 51st in individual. There she also competed in sprint, finishing 87th. Then she missed two World Cup stages returning in Oberhof, Germany. Since the Ukrainian team lacked its leaders (both Sochi Olympic champions Vita Semerenko and Olena Pidhrushna missed that season), she was invited to the relay team. Merkushyna did her job well by shooting without additional shots. Nevertheless, her personal results weren't good enough to debut at the World Championships. Next season she spent in IBU Cup competitions.
On 11 December 2016, Anastasiya Had her first relay podium in Pokljuka, Slovenia. She earned her first World Cup points in sprint in Oberhof. Since then, she has been a member of the national team regularly. She participated at 2017 Worlds, where she showed great achievements for her debut: 10th in sprint, 8th in pursuit, and 14th in mass start. Merkushyna won silver in relay.
She qualified to represent Ukraine at the 2018 Winter Olympics. In Pyeongchang her best achievement was 46th place in pursuit and 11th in relay. In an interview, she was disappointed about her performance and even cried.
Merkushyna studies management and international business at Ternopil National Economic University.
Fellow biathlete Erik Lesser provided his Twitter account with around 150,000 followers as a channel for Merkushyna to transmit viewpoints in March 2022, allowing some 20,000 Russians to see conditions in Ukraine following the 2022 Russian invasion of Ukraine.
|Event||Individual||Sprint||Pursuit||Mass start||Relay||Mixed relay|
4 medals (1 silver, 3 bronze)
|Event||Individual||Sprint||Pursuit||Mass start||Relay||Mixed relay||Single mixed relay|
- *During Olympic seasons competitions are only held for those events not included in the Olympic program.
- **The single mixed relay was added as an event in 2019.
|2017–18||Kontiolahti, Finland||Mixed relay||2|
|2018–19||Pokljuka, Slovenia||Single mixed relay||3|
|2019–20||Ridanna, Italy||Super sprint||2|
|Obertilliach, Austria||Short individual||2|
|2015–16||Ridanna, Italy||Mixed relay||3|
|Arber, Germany||Single mixed relay||1|
|2016–17||Ridanna, Italy||Single mixed relay||1|
- "Ukrainian squad for the 2018 Winter Olympics". Ukrainian Biathlon Federation. Retrieved 20 January 2018.
- "Ukraine professional Merkushyna thanks Erik Lesser". Spot my Sports. 7 March 2022.
- "Olympiad participant exchanged biathlon rifle for machine gun and went to defend Ukraine". Українська правда (in Ukrainian). 13 March 2022. Retrieved 13 March 2022.