[37][38] In August 2008, she went to Eichstätt in which she competed in the German Women's Championships, where she won silver after defeating Silke Huenecke 28–7 and Janine Hoffmann 19–12, however, once proceeding to the final she lost by one point against Nikolina Orlovic 13–14.

2007 2008 After winning her silver medal at the German National Championships, Hammer had briefly considered competing in the 2012 London Olympics, but her ambition to become a super champion was greater.

[43] On 24 October 2009 at the Anhalt Arena in Dessau, Hammer won a four-round unanimous decision over Czech fighter Sarka Stoklaskova, who fell to 2-8 (1 KO) with the loss.

[43] Until 23 October 2010, she went on to have five more fights in the space of eleven months, defeating Marija Pejakovic, Daniela Bickei, Patricia Braesick, Marie Riederer, and Mihaela Dragan all via knockout within five rounds.

[44][45] On 23 October 2010, Hammer stepped up her level of competition and faced Teresa Perozzi for the vacant WBO middleweight title at Erdgas Arena in Riesa, Germany,[46][47] with the fight shown on Sport1.

[43] On 21 October 2011, at the Brandenburg Halle in Frankfurt, Germany, Hammer won a ten-round unanimous decision over American Vashon Living, defending her the WBO and WBF middleweight titles.

[62][63] Living, who was at a significant size disadvantage, was mobile and agile as she attempted to get to close quarters and work inside, but Hammer was still able use her reach advantage to control the pace.

[66][43] The judges Zoltan Enyedi, Manuel Oliver Palomo, and Andre Van Grootenbruel scored the fight 99–91, 100–90, and 100–90 all in favour of the defending WBF and WBO middleweight champion.

[68][69] Hammer came in at 70.3 kilograms, while Hernandez weighed a few grams too much in first gear, to which her manager, Daniel Born, acted resolutely and cut off the boxer's pigtails, which resulted in the weight being corrected to the point.

"[78] The date set for the return would mean Hammer would be fighting on the undercard of Wladimir Klitschko defending his WBA (Super), IBF, WBO, IBO, The Ring, and lineal heavyweight titles against Francesco Pianeta at the SAP Arena in Mannheim.

[83][84][82] It was announced on 14 June 2013, Hammer was to drop the extra five and a half pounds to 157 and challenge Mikaela Laurén from Sweden on 13 July 2013,[85][86][87] on the undercard of Robert Stieglitz's defense of his WBO super-middleweight title against Yuzo Kiyota at the EnergieVerbund Arena in Dresden.

[95] After ten entertaining rounds of boxing, judges Frank Michael Maass, Terry O'Connor, and Alejandro Lopez scored the bout 100–90, 99–91, and 98–92 all in favour of the defending champion, who improved her spotless record to 15–0.

We are similar in size and this fight can be made [...]"[98] On 6 December 2013, Hammer retained her WBO and WBF female middleweight titles with a first-round knockout over Carmen Garcia Toscano at the Brandenburg Halle in Frankfurt.

[101] Within the middle of the round, Toscano could no longer avoid the blows of Hammer and was unable to defend himself on the ropes, which is why Referee Ingo Barrabas intervened.

"[103] It was announced on 27 January 2014, that Hammer was set to make her seventh title-defense against challenger Jessica Balogun on 1 March 2014, at the GETEC Arena in Magdeburg.

[104][105][106] Balogun will be moving up from 147 pounds, but she insisted that the added weight will only make her stronger, that Hammer has never faced anybody with her style, while having full of confidence that she has what it takes to cause an upset.

"[115] In June 2014, it was announced that Hammer would face the former multiple world and European champion Anne Sophie Mathis (27-3-0, 23 KOs) for the WBF and vacant WBO junior-middleweight titles on 26 July 2014 at the Anhalt Arena in Dessau.

[136][137] On 29 July 2014, The sanctioning commission, the Bund Deutscher Berufsboxer (BDB; Association of German Professional Boxers), followed the WBF decision and officially changed the bout outcome to 'no-contest'.

[138][139] BDB President Thomas Pütz apologised for the "bad decision" and stated that there will be an investigation of the said event and a hearing of Manfred Küchler to decide whether he will be suspended.

[140][141] On 7 August 2014, after reviewing the bout, the WBO agreed with the WBF and BDB and declared it a 'no-contest' and did not order a rematch since Hammer is the organization's reigning middleweight champion.

[159][160] Hungarian Melinda Lazar became a front runner to challenge Hammer, to which, on 20 June, it was confirmed to take place at the Ballhaus Forum in Munich on 15 July.

[169][170] The smaller Reis was very aggressive from the opening to the final bell, kept moving forward and had her moments landing hard hooks to Hammer's head and body.

[172] After ten entertaining rounds judges Ed Pearson, Fernando Laguna, and Grzegorz Molenda unanimously scored the bout 98–93, 98–93, and 100–90 all in favour of Hammer.

[182] In front of a crowd of 17,000 in attendance, Lindberg simply could not get past Hammer's stinging jab and the combinations she put together behind them,[183] ultimately losing all ten rounds on all three scorecards,[184][185] with judges Massimo Barrovecchio, Guido Cavalleri, and Eddie Pappoe scoring the fight 100–90 all in favour of the defending WBO and WBC champion.

[191] On 4 November 2017, Hammer retained her WBO and WBC middleweight titles with a fourth-round knockout win over Gifty Amanua Ankrah at the SportScheck Allwetteranlage in Munich.

[205] Hammer smartly exploited her height and reach advantages by keeping the fight at long range but moving inside just often enough to win the majority of the exchanges.

[214] In the post-fight interview, Hammer spoke of attempting to get the knockout, though praising Nelson's toughness, though she continued by stating: "I'm really looking forward to fighting [Shields].

[217] On 25 September 2018, The Ring announced that Hammer and Shields will fight for undisputed middleweight championship at the Adrian Phillips Theater at Boardwalk Hall in Atlantic City, New Jersey, on 17 November,[218] with the winner becoming the second woman of the four-belt era to hold all the titles in one division.

[228] On 12 February 2019, it was announced that Hammer and Shields will meet for the undisputed championship on 13 April at the Adrian Phillips Theater at Boardwalk Hall in Atlantic City, New Jersey, with The Ring female middleweight title also being contested.

[238] She is a brand ambassador for the underwear line Anita, for which she occasionally models,[239][240] while also being a part of Movement130, which encourages females of all shapes, sizes, and lifestyles to embrace their own distinctive beauty.