Home Secretary Theresa May has revealed she has been diagnosed with Type 1 diabetes but insists it will not affect her political career.
The condition means her body does not produce insulin and she must now inject herself with the hormone at least twice a day for the rest of her life.
She told the Mail on Sunday that the diagnosis "was a real shock" and had taken a while to come to terms with.
But it was a case of "head down and getting on with it", Mrs May added.
She said: "The diabetes doesn't affect how I do the job or what I do. It's just part of life.
"'It started last November. I'd had a bad cold and cough for quite a few weeks. I went to my GP and she did a blood test which showed I'd got a very high sugar level - that's what revealed the diabetes.
"The symptoms are tiredness, drinking a lot of water, losing weight, but it's difficult to isolate things. I was drinking a lot of water. But I do anyway.
"There was weight loss but then I was already making an effort to be careful about diet and to get my gym sessions in.
"Tiredness - speak to any politician and they will tell you the hours they work. Tiredness can be part of the job. It is full on."
Initially doctors thought Mrs May had Type 2 diabetes but two months ago it was revealed to be Type 1 diabetes.
There had been media speculation that Mrs May losing two stones in weight over 18 months was linked to a potential Conservative Party leadership bid, but she said this had been partly down to the illness.
Asked if her diagnosis would prevent her from one day replacing David Cameron, she told the newspaper: "There is no leadership bid. We have a first-class prime minister and long may he continue."
She added: "It doesn't and will not affect my ability to do my work. I'm a little more careful about what I eat and there's obviously the injections, but this is something millions of people have. I'm OK with needles, fortunately.
"There's a great quote from Steve Redgrave who was diagnosed with diabetes before he won his last Olympic gold medal. He said diabetes must learn to live with me rather than me live with diabetes. That's the attitude."
Meanwhile, the Labour MP Keith Vaz, who was diagnosed with Type 2 diabetes in 2007, has said it is a "shock to be told" you have the condition.
Writing on Twitter, he said "Mine came 6 years ago. Theresa May right to reveal. 500k have it and don't know. Take the test."