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The Quick Answer

Can you start a sentence with However?

Yes. It is perfectly fine to start a sentence with However. In fact, starting a sentence with However should be encouraged not discouraged. However, if you cannot bring yourself to do it, you can precede your However at the start of your sentence with a semicolon (not a comma) or slide it further down your sentence and offset it with commas. For example:

• I like oats. However, I cannot eat flapjacks. 
• I like oats; however, I cannot eat flapjacks. 
(This quickly gets annoying. Don't overuse semicolons.)
• I like oats. I cannot, however, eat flapjacks. 
(This does not scan as well for readers.)

When however means nevertheless, it is followed with a comma. When however means to whatever extent, there is no comma after it. For example:

• I like oats. However, I cannot eat flapjacks. 
• I like oats. However much I try, I cannot eat flapjacks. 

You Can Start a Sentence with However

For no good reason, lots of writers dislike starting a sentence with however. However, you can start a sentence with however. In fact, starting a sentence with however is a clear way to link a new sentence to the previous sentence, which is the primary function of a conjunctive adverb like however.

The loathing for starting a sentence with however causes lots of writers to use a comma before however and then write a new sentence. This is an error. In fact, it is the most common error associated with however. For example:

• Good leaders must communicate vision clearly, creatively, and continually. However, the vision doesn't come alive until the leader models it. (John C. Maxwell) 
• Good leaders must communicate vision clearly, creatively, and continually, however, the vision doesn't come alive until the leader models it. 
(Using a comma before however and starting a new sentence is called a run-on error.)

It's a Common Misconception with Powerful Supporters

In 2015, British MP Michael Gove (Britain's Secretary of State for Justice and formerly the Secretary of State for Education) sent a note to his staff instructing them never to start a sentence with however. This advice is also included in "The Elements of Style," a popular style guide in the US. However, there is no good reason for this "rule," which is causing writers to litter their work with run-on errors as they opt for a comma before however.

Starting a sentence with However should be encouraged not discouraged.

When To Use a Comma After However

The word however has two meanings. It can mean nevertheless and to whatever extent. For example:

• Religious tolerance is something we should all practise. However, there have been more atrocities committed in the name of religion than anything else.  (Walter Koenig)
(Here, However means nevertheless or but.)
• While conscience is our friend, all is at peace. However, once it is offended, farewell to a tranquil mind. (Mary Wortley Montagu)
(Here, However means nevertheless or but.)
• I never give up in a match. However down I am, I fight until the last ball.  (Bjorn Borg)
(Here, However means to whatever extent.)
• However difficult life may seem, there is always something you can do and succeed at.  (Stephen Hawking)
(Here, However means to whatever extent.)

Here is the ruling on using a comma after however:

When however means nevertheless, it is followed with a comma. When however means to whatever extent, there is no comma after it.

However Is Not the Same As But

Even though the word however can mean the same as but, they are grammatically different. However is a conjunctive adverb (like therefore, consequently, and nevertheless), and it is used to link the ideas either side of it. But is a coordinate conjunction (like and, or and yet), and it is used to join the like-for-like elements either side of it.

Of course, it is possible to start a sentence with but, but this is using but as a conjunctive adverb and not a coordinate conjunction, which works given it means the same as however. Of note, when but is used at the start of sentence, lots of writers like to follow it with a comma to recognize its role as a conjunctive adverb and not a coordinate conjunction.

Using a Semicolon before However

To give a smoother transition between sentences, a semicolon can be used instead of a period / full stop. This means the word however (particularly when it means nevertheless or but) can be preceded by a semicolon. For example:

• Religious tolerance is something we should all practise; however, there have been more atrocities committed in the name of religion than anything else.  (Walter Koenig)
(Here, however means nevertheless or but. It has been preceded by a semicolon instead of a period / full stop to give a smoother transition between the two "sentences," which have now become independent clauses.)

Read more about using semicolons.

Note

I Can't Bring Myself to Start a Sentence with However

If you really must avoid starting a sentence with However because you have some OCD-style aversion to it, then you can usually place it further down your sentence.

When you do this, it is usual (but not essential) to offset it with commas. For example:

• Religious tolerance is something we should all practise. However, there have been more atrocities committed in the name of religion than anything else.  (Walter Koenig)
• Religious tolerance is something we should all practise. There have, however, been more atrocities committed in the name of religion than anything else. 

The practice of sliding your however down the sentence to avoid putting it at the start ought to be discouraged. The best place to put any conjunctive adverb (the function of which is to bridge the ideas in two sentences) is at the start of the second idea.

• 11 [bridge] 22
(This scans far better than the version below.)
• 11 2 [bridge] 2

COMMON PROBLEMS WITH HOWEVER, THEREFORE, AND SIMILAR WORDS

• This page explains a type of error writers often make when using words like however, furthermore, therefore, thus, consequently, and moreover.

  The problem occurs when writers use these words to conjoin sentences. Readers find the error to be distracting because it disrupts their expectation about where sentences should end.

  EXAMPLE MISTAKE

  January may be the coldest month, however, it is a time of great beauty.

  The boldface “however” and the comma after “month” are the problems. This is easy to correct. But first, here is some explanation.

  A common problem writers face is the incorrect usage of conjunctive adverbs. Many times it is because they confuse them with coordinating conjunctions.

  A coordinating conjunction is a familiar part of the English language and includes the following: and, but, or, nor, so, for, yet. A conjunctive adverb is not so common in everyday speech, but occurs frequently in written prose. These include the following: however, moreover, therefore, thus, consequently, furthermore, unfortunately.

  Most of the time, problems occur when the writer uses a conjunctive adverb in the middle of a sentence when a coordinating conjunction is actually needed. But remember that conjunctive adverbs can be used in any part of a sentence.

  This page addresses the problem that arises when conjunctive adverbs are used wrongly to connect two sentences. To avoid this problem, a basic rule to follow is this: If the two parts you are connecting can stand on their own as separate sentences, then you have probably misused the conjunctive adverb. If this is the case, you have a few options for fixing it. Usually a semicolon is the best choice, but you may also use a period or a coordinating conjunction.

  INCORRECT

  Watering and feeding new plants is necessary for growth, however, too much water or fertilizer can kill them.

  Erica felt as if she might faint from hunger, therefore, she decided a trip to McDonald’s was necessary.

  Joyce Carol Oates is a novelist, essayist, playwright, and poet, moreover, she is a distinguished scholar.

  All of these examples create comma splices because there are complete sentences to the left and the right of the conjunctive adverbs however, therefore, and moreover. The commas after “growth,” “hunger,” and “poet” create the comma splices. Here is the correct way to punctuate these sentences.

  CORRECT

  Watering and feeding new plants is necessary for growth, but too much water or fertilizer can kill them.

  Erica felt as if she might faint from hunger. Therefore, she decided a trip to McDonald’s was necessary.

  Joyce Carol Oates is a novelist, essayist, playwright, and poet; moreover, she is a distinguished scholar.

  Notice that the first example replaced the conjunctive adverb with a coordinating conjunction, the second with a period, and the last used a semicolon. Because many of theses parts of speech can mean basically the same thing, it is tempting to use them the same way in a sentence. Just remember: coordinating conjunctions can conjoin sentences. Conjunctive adverbs cannot. This may be a bit confusing, but with practice and a sharp eye you can avoid making this common mistake.

  by Athens Battles

  Examples for this handout were adapted from:
  Rosen, Leonard J., and Laurence Behrens. The Allyn and Bacon Handbook. 3rd ed. Needham Heights, MA: Allyn and Bacon, 1997.

https://www.iup.edu/writingcenter/writing-resources/grammar/common-problems-with-however,-therefore,-and-similar-words/

http://www.grammar-monster.com/lessons/starting_a_sentence_with_however.htm