In the dark, dull weeks of January many of us are donning lycra or dusting off the juicer, but what about our financial health? As Big Ben struck midnight, many of us will have promised ourselves that we would be better with money this year. If you were among them then one simple thing you can do is sort out your investment portfolio.

Here are five things you should do to make sure your investments are fit and healthy in 2015.

Not all fund supermarkets are the same: they have widely varying charging structures. Last year many of them changed the way they charged their customers, so it is well worth taking a look at how you are being charged to invest, and whether you could get a better deal elsewhere.

As a rule of thumb, those that charge a percentage are better for first-time investors or those with less than £100,000. Investors with larger sums will benefit from paying a flat fee, says Kyle Caldwell in The Telegraph.

When you started investing you could have been in a very different stage of your life and chosen your stocks and funds accordingly. Take a moment to think about what your want to achieve now, has it changed?

If you are approaching retirement do you want to think about starting to move your investments into lower risk assets in order to avoid being stung by a sudden crash? Or are your investments not growing enough to achieve your goals, should you consider switching to a higher risk strategy?

Investing is a ruthless business and that means you need to be prepared to dump investments that are not doing their job. Many of us hold on to some investments for sentimental reasons – a family member worked there, they were one of our first investments – or simply because they’ve gone down but we don’t want to crystallise our losses. These are incredibly bad reasons to hold onto dud stocks or funds.

Three consecutive years of underperformance should spark an alert, says Darius McDermott, of Chelsea Financial Services, in The Times. Take a clinical approach and look at each of your investments in turn. Are they performing well? If not, is there a solid reason why you believe they will recover? If the answers are no it may be time to sell and get into something more profitable.

It isn’t just the poor performing stocks you need to take a look at. Investments that have done particularly well could be throwing your whole portfolio off kilter. For example, if you hold biotech shares or funds they have soared in recent years meaning you could now be overexposed to the sector.

Take a look and if one area of your portfolio has ballooned consider selling some of your holdings and ploughing the profits into another sector.

®Andrew Burton/Getty® Investment: how to refresh your portfolio for 2015

Not only will this reduce your risk, but by selling investments that had done well in favour of those that had fallen, investors were effectively selling at the top of the market and buying at the bottom, says Patrick Connolly, a financial adviser for Chase de Vere in The Telegraph. This is the holy grail of investing and something which very few investors consistently achieve.

Finally, take a look at where you are holding your investments. Have you maxed our your Isa allowance for the year? You can invest up to £15,000 via an Isa this tax year. If you haven’t used up your allowance consider shifting your portfolio so more of it sits within your Isa and you can avoid paying tax on your profits. ·