BERLIN (Reuters) - German dialysis specialist Fresenius Medical Care cut its 2018 sales target due to lower than expected doses of calcimimetic drugs at its dialysis service business in the United States.

The company said on Sunday it now expects sales to rise by 5-7 percent at constant currency, compared with a previous forecast for a rise of around 8 percent.

Calcimimetic drugs, which are given to kidney patients to control calcium levels and prevent hardening of the arteries, were given in tablet form until the start of this year, but are now available as an injection.

That means there is a change to how they are reimbursed by Medicare and so FMC has had to shift the drugs from its pharmacy business into the dialysis service business.

However, dosing of the drugs in the dialysis service business was lower than FMC had expected because patients were taking it more accurately than before, meaning revenue did not rise as planned.

"Due to a faster than expected reduction in dosing of those drugs in the controlled clinic environment, we are experiencing a headwind on revenue growth for fiscal 2018," CEO Rice Powell said in a statement.

It confirmed a target for 2018 net income to rise by 13-15 percent at constant currency.

It also reported preliminary first quarter results, with revenue up 2 percent at constant currency to 3.98 billion euros (3.5 billion pounds) and net income stable at 279 million euros.

FMC had on Saturday announced the sale of Sound Inpatient, a U.S. provider of emergency medicine and critical care. It said on Sunday the 2018 targets did not include the effect of the disposal.

It is due to report full first quarter results on May 3.

(Reporting by Victoria Bryan and Caroline Copley, editing by David Evans)